What should I do

I’m just really sad an depressed I had sex with my boyfriend jun 24th he didnt cum in me but I was ovulating he pulled out an he got the Sperm all over my libia...I got a positive pregnancy test today an he was upset he said he don’t think the baby is his because he didn’t come in me 😔 I haven’t had sex with anyone else just feel so alone idk y he think I would cheat on him idk what else to do man