How many female friends? I'm sorry but this is a little fishy no pun intended. Girls are scandalous and guy's like the fact that there are girls around just in case they need to sleep with them, or if there current relationship does not work out.
I am not saying he doesn't love you or care about you. But there is a difference between healthy friendships and not. Ask yourself these questions.
Are these girls nice to you?
Do these girls pretend your not there in front of your boyfriend?
Does your boyfriend lock his phone or talk to his "friends" only when you out of the room?
Have any of these women had sex with your boyfriend?
How many times a day or week does he use facebook, myspace etc. to contact them?
Would he be cool with you having just as many guy friends?
Humans (especially women) are born with a strong gut instinct. Your not crazy. Something in your body is turning on the fire alarm. I personally wouldn't be cool with it, especially if my gut was telling me something.
People can say "your just jealous" all day long, but the truth is if your heart, mind, and gut were telling you this is ok then you wouldn't be paranoid. Life is short.
Follow your gut we were born with one for a reason.
All this "la di da da" denial about saying it's normal to feel like that is bull shit.
It's not normal for your boyfriend to have a string of girls that are his friends if it worries you.
Don't Ignore your suspisions about this or anything else. We have one life to live don't waste time.