If you have the slightest feeling to not have sex, then you probably shouldn't, you'll probably end up regretting it. But if you go for it just make sure that hes the one for you, make sure you guys are really, truly in love first.
There's no right time to start having sex in a relationship, it's different for every couple. If you both wanna have sex you should do it. Start slowly and see how it goes, if you realize your not ready just tell him.