Just because a girl tells you "you look nervous" is not a reason to seek medication or to feel like you need any. In fact this is a great way to get more involved in the conversation by smiling and saying....No, not at all and I don't mean to come across that way.....I'm just listening. Most guys are a little nervous when speaking to women, but you have to just be yourself and they will accept you for who you are. Some women think they're intimidating and will play on this and maybe "think" they're making a guy nervous. Hold your head high, make eye contact and say what you have to say and smile often. This will show confidence and make others see you as more approachable. You're not nervous so I doubt you appear nervous, just don't take this so seriously, it sounds like you are a healthy male. Hope this helps.
If you feel fine there is definitely no need for meds. You actually may just be a bit awkward in front of women. Most guys are and most women know it. They often pull that card just to make conversation. In fact they are probably nervous themselves. It's very normal to be a little out of your comfort zone when meeting those of the opposite sex. Don't sweat it!
I really appreciate the responses. Maybe I just need more exposure to women.
If you're not suffering from terrible anxiety in these situations, you absolutely shouldn't be thinking about medication. All you need is experience and honesty. More often than not, young women will project their own feelings to attempt to interpret yours. This is normal and healthy, and a normal and healthy response is to be honest. If you're not particularly nervous, say so (which is a positive thing, btb; being confident and relaxed lets you be yourself and enjoy the situation) and feel free to ask next time why exactly she has the impression you're nervous. Chances are, in doing so, you can learn a lot about her in the process.
Anyhow, you don't need medication to meet other people's unrealistic impressions.