Is Ex-Sex right for you?

My ex and I split up about 2 and a half months ago after a year and a half of being together. We broke up because he wasn’t taking our relationship seriously enough for me, canceling plans at the last minute and not being attentive. He is only the third person I’ve ever slept with. I know he’s seeing a couple people casually now but I haven’t been seeing anyone and I’m getting lonely. The last couple times I went out to the bars I really wanted to call him and see if he wanted to just hook up. My friends have talked me out of it, but I don’t think it’s a bad idea because I know it’ll be good and I feel safe with him and it’ll keep me satisfied until I find someone new. Who’s right?”