had unprotected sex with two different partner now I am pregnant

first I like to say I'm not proud of myself and I never though this could happen to me but a guess it can happen to anyone. Well I am 38 pregnant and I had sex with my boyfriend on December 24 before my period was supposed too start it started no the 27 but I came light and a bite clear and it finished in 5 days normally it would finish in 7 days then in January I had sex with my ex on the 22 and the 23 , 3 days before my period was supposed to start . And it didn't start and I didn't start have pregnancy symptoms until the 15 of February... Now am not sure who is father is there a possibility that it could be for my boyfriend are is my ex ... I really need your help I would really like to know opinions please