Maria, it sounds like you probably don't have your bike "dialed in" for your body fit. I would suggest that you get a professional bike fitting. You say you have a Trek and I noticed you're from MN - if you bought it from Penn, chances are if you took it in to the shop you bought at it and told them you are new and having trouble adjusting if for proper fit, they would help you free of charge or very little charge. Also, Erik's does professional fittings for a reasonable price (I think I paid less than $30 several years ago).

One last thought re: the elbow pain, I wonder if you're not gripping the bars too tightly and/or using too much of your upper body instead of letting your legs and core do most of the work?