Help me!

Yesterday I went through so much shit. I found out while on my boyfriends computer he was messaging his friends telling them I’m “lame and not all that” and then he said I was just “real and has hella respect for me” that’s not even the worst part. I was in his emails and I found out he’s been posting Craigslist ads looking for m+t. He posted his dick in the picture, he’s been cheating on me our whole relationship. He came home I left it up on his computer of course said he didn’t know what it was and nothing even happened blah blah. I left him of course and right after he starts blocking me on everything. I don’t know how to feel. 9 months with his guy him telling me he loved me we had plans to move out in literally less than a month. We were friends like 5 months before dating I don’t understand why he didn’t just stay friends with me instead of doing this to me. We got along so well like best friends. I’m so confused and I feel so used. Idk what to think. I’m trying to be strong but this feels so hard. I never saw this coming. Any advice please??