Is it normal that i might be in love with two girls?

I have been in a great relationship with my current girlfriend for about four years now, and we have lived together for over two years. Everything used to be great, and I felt special everytime I woke up next to her.

However, recently I have met another girl and even though she is the complete opposite of my girlfriend I am extremely attracted to her.

My girlfriend is a smart, independent, educated and succesful business woman with dark eyes and hair (which is what I am usually into, since I am not looking for a woman to take care of but a woman that challenges me). But this other girl is a blonde that comes across as caring, loving and sweet.

Myself and the blonde have been spending a lot of time together, and even though we are both in a serious relationship it is obvious that there is a lot of chemistry between us.

Appearance wise they are both incredibly attractive compared to me. And to be perfectly honest, I would like to mention that I am not a very attractive guy, I work out a lot and am very fit, but my (lack of) hair and my not very manly facial features (I have a very round head and small eyes to match) generally do not make me eye-candy to most women.

At this point I am just confused about the whole thing. I have come up with a number of scenario's which to me all seem plausible and I would like to know which one suits my situation the best.