Suggest Suitable Condom Size Which Can Offer Comfort

Okay so my girlfriend and I plan on having sex for the first time this weekend and I went to the store to by condoms. I went with Trojan spermicidal specifically just because it seems to be safer. Well being a virgin I decided to go ahead and practice with one of the condoms so I can get better at the whole process. After following the instructions I felt that the condom was rather tight and didn't fully unroll all the way down to the base of my penis. The thing is the condom seems to be plently long enough its just too tight and wont go down all the way. Is this a problem ? Should I go ahead and buy a bigger sized condom?