Help anyone

I'm 19 a male and at the end of my rope

I have another post explaining my situation to sum it up I had girlfriend for 2 years she got pregnant has the baby I propose and one and a half years later we have a daughter I've done so many things for her no matter what and I moved our family into a trailer with me and my brother and a few months later she broke up with me saying she needs time out of a relationship and she needs to focus on herself and 4 days later I find out she has feelings for my brother we are gonna be co parenting here in separate rooms that was the plan moving forward and even as hurt as I am I can do it just to stay with my daughter and have time with her but my question stands...what do I do and how am I supposed to feel my brother has agreed that he will draw boundaries and will not pursue her until I'm healed but he said too that if time passed that it shouldn't matter and that logically if it was him i could be certain shed be with someone who has my daughters health in their mind at this point I feel so hurt and betrayed I don't know what to think or believe my thoughts are to stay here try to heal so I can just get passed everything sooner for my daughter I have to become whole again it's just so hard when she tries to act like nothings happening and I have to act the same way this is so fucked please someone tell me something I'm 19 I sacrificed everything to get here and I don't know what to do anymore I'm in a dark place guys this weed and liquor is only going to make it worse but it's the only thing that feels right anymore I want to be here for my daughter so I can't let the dramatic things happen and my daughter is all I have left please help