M.B.
It can take quite some time for your hormones to get back to normal so your periods will be regular again. BUT, as you noted, you can still get pregnant because you can ovulate before you get your periods back. Also, since you did not gradually wean, it likely is taking longer - with the milk production being a sign that you still have elevated prolactin, which can suppress your periods.
Mine came back with both my sons when they were 18 months old (and still nursing a few times a day). Apparently, it's the nite time nursing that most impacts when your periods return. Also, it's different for everyone.
Why don't you just go buy a pregnancy test if that's what you're worried about?