I wouldn't really call it an obsession but if you do, then it might be a problem.

I have an obsession with Rainbow Dash but, it's not a big obsession.

Why would you need 300 pics of Trixie?

Why would you need 300 pics of Trixie?

*3000

I jokingly named my ThinkPad T60 Trixie.

Tsixty. lol

Oh god, I do that all the time too, except with Pinkamena, I can't even type my username sometimes

Trixie Trixie Trixie Trixie Trixie Trixie...Trixie.

everybody does it, mostly not with ponies, but everyone does it. i wont lie, i have the same problem with luna, but i learned how to deal with it.

As long as it doesn't start physically affecting you for the worse, or if it causes you to do something incredibly stupid.

But then you said your grades are dropping due to your obsession. I really don't see why you need so much Trixie art, so I would just try to limit that. Of course that may be much harder than it sounds, and I can understand that. But I believe it would be for the better, if you try not to spend so much time collecting more images, and obsessing over Trixie as much as you do.

Not that I'm saying your obsession is bad, but I would try to not let it interfere with what's more important.

I used to be obsessed with Wheatley but I got better. Still love him though.

Yeah... I have the same problem with Luna... I have a similar number of pictures stored on my computer, sometimes I'll sign my name as Luna at school, but the teachers just take it as a joke XD And I've purchased hundreds of dollars worth of Luna merch.
Obsession buddies! *Internet high five* 

I wouldn't say your obsessed to bad. I would just try and not let it bring your grades down though. I mean there is nothing wrong in liking something a lot just don't let the thing hinder your daily life.