What should i do?

my boyfriend of 3 years recently got a new job @ Walmart. we recently got a new house together and he was talking about getting engaged and then suddenly it all stopped. he didn’t talk to me for 3 days and constantly stayed on his phone. i knew something was up so i went on his phone while he was in the shower and found out he was texting another girl. i confronted him about it and he said it was just a friend from work. i genuinely was hurt. he said that they were just friends and he needed someone to go to to talk about his problems. and that made me hurt even more. like why couldn’t he come to me for his problems instead of some girl he was working with. about 3 days go by and we get into a big argument and he brings up maybe we need to see other people. and i bring up i really think this is funny since you just started talking to this girl and all of a sudden you want to break up. and he calls me paranoid but if any of y’all would see this girl, y’all would understand. we just blew each other off. then the next day we’re talking and i tell him it’s okay. i understand that he doesn’t feel comfortable talking to me about his problems anymore. then he tells me he likes her. and she likes him. and now i’m just heart broken. he said he wanted us both and doesn’t know what to do.

what do y’all think i should do? i’m hurt, heartbroken, and just overwhelmed. i love this boy with all of my heart. we are high school sweethearts and i’ve known his for 10+ years. i just need advice.