Is it normal to have a sexual obsession with women's underwear?

I love panties. I love how they come in so many shapes, colors, textures, fabrics and styles. During sex with my girlfriend I prefer she leave hers on and I simply slide them to the side for access. When giving her oral it's not uncommon for me to lick her through her panties. The texture of the fabric on my tongue as well as the taste of her vagina is a real turn on for me. I should also note that she loves my little fetish. She models her panties for me and gets aroused when she watches me admire and obsess over them. I even go to Victoria's Secret every now and then and buy myself some panties to masturbate with (physically using them around a my penis as well as simply holding and caressing the fabric with my hands for the extra sensory stimulus). I prefer to buy size XS because it also adds to the fantasy of being with younger girls. I currently own about 12 pairs, all different styles and colors. (Please note that I do not WEAR panties, I just use them for sexual fun.