Birth Control

I am 26 years old and have never been on birth control. If I have sex me and my partner always use a condom and it's been very affective so far.... in the last 4-5 months I have been having problems with getting cysts on my right ovary that cause a lot of pain during my ovulation week... currently we are not trying to conceive... I was told by my dr that birth control will help with the cysts... I am willing to try for 6 months to see if it helps... I am curious about what brand I should use... I don't know a whole lot about birth control but I do know that I want to take the pill... are there different types? Which ones causes the least amount of weight gain... (I struggle with my weight already) and how accurate is it that I won't get pregnant.

Thank you in advance for any advice!!