Wacky periods??
Yep. It's completely normal. It will take some time for your hormones to stabilize and you should become more regular as you lose more weight. I say "should" become regular because some people might have some other condition causing the irregular cycle but ususally that would be a problem before the surgery as well. I'd say to give it some time and see if it straightens itself out.
No, you're normal...these things get crazy post-op due to all the wonderful hormonal changes going on in our bodies - you may (or may not) experience more cramping and back aches than before as well. They should stabilize in a couple of months, but for now you just never know when or where it might show up - lovely, huh.