Ah.
3 PPAFs at 17 months PP - that's pretty good.

14 months is average for periods to return, or so I hear...
Is he nursing at night yet? Some times it is night nursing that makes the big difference. Once my baby dropped to one feed a night that is when my periods came back - but they were all screwed up and I don't know if I was O'ing... not paying too close attention, not TTC - just thrilled that woo hoo, 3 in a row, regular!!! Then the 3rd one didn't want to end...
Anyway... at 17 months I'd say give it a try. I have heard of ladies who took clomid while nursing and it was successful. The biggest drawback, really, is what happens with your hormones - it can affect your supply, and then pregnancy of course dries some people up altogether, but at 17 months, it's not a huge deal, so long as you are OK with it. He's able to get enough nutrition from other sources that this isn't a problem from that standpoint. Comfort is another issue but to be honest... I weaned my son at 14 months... I thought he'd be devastated... he took it very well. He took it a little too well, really... it was rather insulting.
Personally I think you'll be fine.