Is it bad if my little finger sometimes locks up when im playing? When it happens should I take a break or something?
If you've been playing for 10 hours straight and this happens, I'd say yes. How long do you have to play to have this happen?

Oh, btw, I'm not a doctor, but I play one here on this forum.
Don't push through the pain barrier while practicing, you'll do more harm than good. Eventually you'll get used to it. Try playing looser (this allows more speed as well as stamina)
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I had been playing nonstop for about 2 hours practicing my sweeps on my les paul, and when i made a reach with my little finger from 12 to 17 on the little e string and it just sorta locked up. Didnt hurt just kinda freaked me out and then i started playing agian and it happened about 10 minutes later and then i stopped. I didnt hurt it just felt weird.
yeah i have the same problem.

but the thing is, it locks up ALL the time.

I can't even play bar chords properly without taking my strumming hand to unlock it...
...Have you warmed up properly?

I used to get uncooperative fingers all the time before I learnt to warm up... just play through some scales slowly, picking every note at even tempo (2 or 3 notes/second). That and slow improvisation/chords. Shouldn't be shredding until you've done at least 10 minutes of slow stuff, of course working up to it as compared to jumping up to twice the tempo. The general rule for me is to never move (up or down)more than 10% of the tempo/notes per second I'm playing in one step.
This happens to me for several reasons, like playing too much, sometimes a break is all you need. If it's cold out or i haven't warmed up yet my fingers wont respond as well. I'm also diabetic, when my bloodsugar gets too high my joints start to lock up, especially my hands, if I have a band practice or a show coming up it's very important that i keep my bloodsugar in check, so that i can play normally.

I can't stress enough how important this is for diabetic guitarists: High bloodsugar is one of the biggest challenges ive had playing guitar. When i practice a part of a song for hours, then try to play it and my hands just don't respond the way they shouldn because my bloodsugar is too high, I get very discouraged. It's one of the most demoralizing things I've had to deal with, and it makes me feel like all the time i spend practicing is wasted. But it's not, and to anyone else in my situation, don't let it get you down, just keep an eye on your levels, and keep rocking.
ive always been able to lock my fingers in particular my ring finger, left hand so, i can keep the finger straight but move the last joint(tip of my finger down) sometimes when i bend a note pretty far up and apply a lot of pressure my finger locks up sometimes causing pain if it happens multiple times.

do you guys think i could potentially develop arthritis? have any of you had this problem?

It's like sports. When you run for a long time, expect your legs to burn. You have to work through a little pain to get better. However, it is okay to say, "Oh shit this hurts," and stop. This is especially true with your hands and wrists as they contain extremely complex networks of small muscles, tendons, and ligaments that you don't use on a daily basis like you use your legs, knees, and ankles when you walk or even stand.