Walked in on my child's father having sex with a girl on MY BED and I believe he's having sex with his stepsister

THIS IS LONG IM SORRY!!

ps. Sorry for grammar and spelling mistakes.

I really needed to vent...

My baby daddy and I broke up last Tuesday (09/17), meaning a week ago from today (09/24). We were together for over two years and I am 8 months pregnant with our first child. A little background information: He is a good person, but very selfish, a terrible friend, and boyfriend. I truly honestly should've been left him as I constantly begged for him to hang and talk to me. He also works out of town a lot and has cheated (sexually once, caught up talking freaky with females more than I can count). Moral of the story is I'm dumb for staying. But not as dumb as whats to come...

The day before we broke up he hit up this girl (lets call her Alice) and told her happy birthday and they ended up having a conversation... the next day we broke up. We live together and I left the apartment when we broke up to give him space. I left the house with what was on my back and another outfit. I didn't expect for us to stay broken up. A day later I ended up in the hospital because since Sunday (09/22) I couldn't keep fluids/food down, I fainted and was having contractions. I was in the hospital for three days. He didn't come to visit me one time. He told me be was on his way or kept making excuses when in reality he was having sex (mind you two days after being separated) with Alice. I was released from the hospital and the next day I decided to get some clothes from the apartment as it was the middle of the day, and again, I had nothing with me. I walk in my apartment and see a girls shoes and bag on my living room floor... I then head to the bedroom.... I literally walk in on HIM FUCKING ALICE ON MY BED, ON MY COMFORTER, ON MY SHEETS, and ON MY TOWEL as she was on her period!!! I took a photo of their faces as they got caught. He told me to get out, and was yelling at me like its my fault he got caught like boy we BOTH pay these bills, I am ON the lease, and all this furniture is LITERALLY mine. ( most of the furniture I brought from my moms house ) . Alice had the audacity to ask me to leave so she can put on clothes, i told her this is my damn apartment. At this point I'm in disbelief this is 4 days after we broke up and there is a random ass female in MY bed. And he disrespected me in front of her. Im 8 months pregnant. I couldn't believe it. He also took off the bloody ass condom, left it on the ground and kicked it and had the nerve to try to push me out the room with blood on his hand and i told him to not put his nasty ass hands on me. He texted me later and told me that he will "take custody" of our son. In which i told him, good-luck, only one of us who can pass a drug test is me (he smokes weed) and there's nothing that makes me an unfit mom. The girl was apologetic but fuck her apology because she knew what the fuck was up.

Now, on to the stepsister situation...

Three weeks ago, his stepsister came into town from Las Vegas to live with her mom and stepdad. You're probably wondering, thats just his stepsister, yeah I figured that too although she is a complete stranger to him. Never spoke with, hung with, or met this stepsister until recently.. all he knew was that she existed but she had problems with her mom and hasn't been in her life in 18 years. My child's father never went over his dads house every day until she came into town. The moment she came into town they exchanged numbers. (Not the problem). She started blowing up his phone, i mean calling and if he didn't answer she would text, if he didn't answer that text she would text again. What she was texting was "are you coming over" ,"when you coming over" ,"wanna chill". You might be thinking still, thats just his stepsister, and you right it is... I felt in my gut something was up. He started to go over there everyday or bring her and her brother to our apartment everyday. Either way, they saw each other everyday. I became suspect when I found out he was deleting messages between them. She would tell him "don't tell Gillian what I told you", and "delete our conversation thread". He also sent a picture to her and deleted it but since she reacted to the photo it still said "blank liked the photo" if you know what I mean on Imessage (blank being her name). I asked him what the picture was and he said it wasn't a big deal, the fuck it is a big deal.

Anyways fast forward to now, we are broken up now. I looked at his phone the other day and he texted her at 8:40pm and said "lowkey im just tryna fuck" she didn't respond and at 9:20 he said "im fucked up right now and meant to send it to a number similar to yours" which makes no fuckin sense. Our area code is 248, her area code from Las Vegas is 702. The following day I knew she was at our apartment and assumed her brother was there too... the morning after that I see the stepsister is on snapchat wearing a shirt that looks exactly like mine. I stop and I'm like wtf cant be. We still share an apartment and I left for some days... I asked him today if he gave her one of my shirts he said "yes" i said why he said "jay (his friend) was coming over and she didn't have a shirt on" i said "what you mean she didn't have a shirt on" he said "exactly that" i said " so she and you was over here alone and she didn't have a shirt on" he said "she had a sweatshirt and she was hot" so I'm dumbfounded now, he knows i don't like this girl and gave her one of my shirts. Why couldn't he turn the AC on? Why was her shirt off? They just met? This at this point answers my fucking question.