I remember on one of my first triathlon training rides, feeling like i needed to puke but didn't want to stop. I had to think in detail how to puke and keep riding and get as little puke as possible on the bike and myself.

But the thinking about all the technical aspects must have distracted me enough to keep me from puking.

well, this is really a running story, but I think it applies. I went from couch potato to exercise by running (went on the cycling later). I started with what I call the "Mail Box Plan" this means that the first day I ran from my house to the mail box. (I live in a little neighborhood with one quarter acre lots), rested a day and then ran from my house to the neighbors mailbox. I added mailboxes til I got to a mile and then kept adding from there. after 2 miles it got easier, cause I was in better shape.

the moral is to just keep plodding onward. try to add a little each time, even if it's just 2 or 3 minutes more than your last outing. try to go out at least every other day.

Do take the bike to the shop for a little tune up.

Good luck!!