Online Dating Blog

i was stupid and signed up for an online dating site and met a guy who i thought was nice. we started using yahoo messenger and talking via messenger and web cam. he did stuff that made me uncomfortable like show me him jacking himself and stuff. the last time we had a conversation he got really mad at me because i wouldnt show him my breasts so i deleted the messenger and my online account to the site.
its been a little over a week and i went on yahoo to check my mail and an instant message showed up from him which i didnt know you could do. he said “hey beautiful its been a while. what happened? you just disappeared off the face of the earth.” i didnt message him back and blocked his name but then today i got a message from a different name and it was him saying “hey baby how are you?” i clicked out of that one and couldnt figure out how to block it.
what do i do he keeps trying to get in contact with me it’s freaking me out. do i delete my yahoo account? (that would make things really hard because then id have to change it on all of my accounts and all of the other things my address is put down for that i dont even know how to change)
(btw im 18 he’s 21)