This is going to be long and boring and I may get flamed but I am so desperate, skip to bottom if you're not interested in the backstory.
I'd been chatting online to a nice bloke for a couple of months (there's a big age difference, I'm 18 and I accept that I'm also an idiot.) We saw each other a few times, talked late every night, we talked about how to regularly see each other, Christmas plans and all that jazz. He told me how amazing I am and how we ~emotionally connected~. Idiot self agreed to unprotected sex because I am on the pill which has served me well for a long time but has chosen the most inconvenient time to fail. When I told him I suspected I was pregnant, he told me not to be daft.
The first time we saw each other, I got some abusive tweets/facebook messages off someone claiming to be his girlfriend, he showed me texts saying they'd broken up a while ago over something petty and their relationship had been a standing joke for a while and he hadn't thought to mention her. This continued and he told me to ignore it, so I did. Obviously upsetting but I believed him. There was a few incidents with her acting oddly including breaking things in his house in a temper.
The last time we talked, I had stayed at his house overnight, he stayed in bed late for a cuddle and left me a key so I could sleep later and let myself out. We planned our next sleepover, and then he stopped answering. I waited for a message for a couple of days, only to find out that I had been blocked on all the ways I had to contact him, cue drunken crying in Wetherspoons. I posted a note through his door asking for an explanation as everything had seemed fine prior to this. I got back a message from his girlfriend telling me I'd just been a quick shag, he didn't want me, don't come to the house again etc.
TL/DR
Blood tests confirmed pregnancy, I suspect the father doesn't want to know, should I attempt to let him know? I don't think I want to carry on with the pregnancy but everyone seems to be telling me he has a right to know.