Sex partners and pregnancy

So I’ve been really stressed out and feel awful. Beginning December I had sex with my long term bf at the time a day or two before I got my period. But my period only lasted about 3 days when it lasts 6-7 and it’s always regular. We ended things and late December I slept with someone else... I’m pregnant and due date is the beginning of September. I’m unsure of who the father is and I’m really depressed. Please no negative comments just need opinions?