Is it normal to masturbate to facebook and instagram pictures?

Is it normal to masturbate to Facebook and Instagram pictures of girls? Now a days girls are pretty revealing always posting pictures of their butts and boobs.

One day I was flipping through Facebook this hot girl I’m friends with posted a picture on the beach laying on her stomach in a thong bikini you could pretty much see the outside rim of her asshole I instantly had a huge boner fighting to get out of my briefs. So I said screw it jerked off to her picture it felt so good.

I came back to her picture a few times then starting looking for other hot girls I’m friends with now I’m hooked don’t even look forward to porn just Girls I know in real life. I do know one other person that does this and the only reason I know this is kinda weird.

My work friend came into work one day in the morning and after the first few minutes went to show me something on his phone the last thing up was Facebook and it was a picture zoomed in on my girlfriends butt bent over in yoga pants she was known for having a huge butt in school everyone knew it but still we worked together I had just enough time to see it and it refreshed I never said anything I was more in shock lol. But anyways is it normal? Serious replies please