Hey community, I'm having odd second thoughts about my sexuality. What's the deal?

[Trusie]

K so I'm a 17 yr. old guy. I've had one serious girlfriend in the past, who I still love dearly, and have fooled around with plenty of girls. I've always been into girls and love checking 'em out and everything, but lately I've been noticing myself exhibiting odd behavior that's been causing me to question, ever so slightly, my sexuality. I have no sexual attraction to guys nor any emotional attraction outside of friendship. I'm wondering if this is a normal thing that someone my age could expect to experience. I have insecurity issues and over analyze every thing around me including myself. Could this feeling be a product of my insecurities (based around not being good enough for my ex, and therefore any girl) and then me over thinking small abnormalities that I observe within myself? Any help, answers, sympathy, etc. is greatly appreciated. Thanks