Pregnant Or Not

On December 18th I was supposed to start my period, but I didn't. On December 19th I had unprotected sex both vaginally and anal. He came in my butt, but I'm not sure if cum got into or on my vagina then. There was also pre too. That day I only had a three percent risk of pregnancy according to eve. After we did it, I went to the bathroom and there was light pink on the paper and again two hours later. On December 20th I woke up to a gush and blood had went through the liner and up the back of my panties through them to my pants. I had a huge spot of blood. The bleeding was heavy that day. After that day I had normal bleeding for the next three days, so I bled four days in total which is the usual length of time my period last. After it ended I had brown discharge for a day or two, but most times have it for longer. My period is now due again in five days, but I'm scared it won't come. I also have been constipated, I have gained a pound or so since over the last few weeks within a few days of each other maybe because I been eating more and not exercising, and having some knots in my stomach and I don't know if they are hunger pains or cramps. My stomach has looked bigger lately, but it could just be because I'm constipated, bloated because my period is due in the next few days, just getting bigger cause I eat and sit there most days now, or maybe I am pregnant. Maybe all three or four reasons. I don't think you gain weight that fast and get bigger in three weeks though. So could I be pregnant or not? I just need some advice on this, please help me figure this out.