When first starting to ride, you may experience some discomfort, but should not be anything like you're describing! Lots of good advice given above. I'd say go to your local bike shop and have them take a look at you while on the bike. They should be able to help you with fit and adjustments, and perhaps recommend a good saddle. Padding may also help-if you don't want to go full bike shorts with a chamois yet, you could look up Adiamo-they make padded briefs that you can wear under regular running shorts. And while I'm talking about clothing, don't wear "regular" type clothing with seams or pockets, anything under your butt that may push into it when seated.