Advice please

I need some advice. This is my 3rd baby i have 2 sons with my partner of almost 5 years. We've had our problems with cheating. Well i cheated in a sense ( i was mentally done and so was he) i slept with a ex 6 days after our last time together. Im now 17w6d with my 1st girl. I honestly dont know for sure who she biologically belongs to but im 85% sure shes my exs due to dates and my doctors opinion. Well he has been pressing a relationship i dont want. Last night he told me she will be living with him and he will be the one whos in the room with me. I ignored the room comment because i already decided my mom will be the one in the or with me not either guy. What got to me was him threatening to take her from me. I wanted to be civil to both as both knows its a possibility either way until dna is done. Now i dont really want to do a dna just because of his threat. Im not a bad mom or anything like that he just wants her. Im not to sure how to handle this situation now. Im terrified of him taking my little girl away. He has multiple issues with alcohol and drugs. He also has a very abusive ex who he takes back every time ( reason why our relationship ended). She absolutely hates me for being with him over 5 years ago. He has become very controlling to the point he would video call me and ask to come over just to see if my sons father is here at my house. He gets mad when i don't answer and tells me im lying every time i try to explain myself. I don't want that negatively in my life. He wasnt like this when we possibility created her. Once he wanted a relationship it started.

How should i handle this. Should i cut him out due to the threat.

Do i remain civil and do the dna for him or just my sons dad.

My boys dad has offered to claim her as his no matter dna. I honestly have no idea what to do or where to go from here.

I also understand i was wrong from the beginning i dont need to be told this. She was also a complete accident but is very much wanted and loved already.