The other guy... help please

Me and my partner were together for 13 years and in those 13 years he has cheated on me 4 times we have now called time on the relationship for good and ive been single for 3 months now. I have been in touch with a old friend who was also a ex boyfriend and we ended up sleeping together 7 years ago it was mistake he was with someone and so was I but I guess we were feeling lonely and I had just been cheated on so feeling insecure. The thing is the day after my relationship ended I started talking to him again and to start off with it was all nice and he called me babe and princess and gave me advice but it quickly turned into something more serious dirty text pics vids and him saying he was going to come see me. I have offered to meet him and bring him to mine and he said he was tired, he works nights so is often very tired. my problem is that over the last week he has been off its me texting him and the flirtiness has stopped and it was more texts with him saying he couldn't be bothered with anything anymore and he was tired and not feeling normal, its now been 5 days and he wont take my calls or reply to my msgs and ive asked him quite a few times for him to text me just to let me know that he is fine its gone from a talking everyday to him not getting in touch at all. i'm confused is it over or do I need to give him space he know I like him and everything was going fine I just don't understand why he is being cold.

I don't want to sound really judgmental arggh because I obviously don't know this guy but from this post it kinda sounds like he's been using you.. sorry D: I might be like completely wrong, slap me if I am, i don't mean to offend/ shit stir