Hi... for a while I've not been able to open my mouth completely and when I try the right side of my jaw hurts. Its also weird when I try and move it side to side, the right side of jaw feels... I don't know.. tight maybe. The left side is fine. I feel like when I open and close my mouth, my jaw feels a tiny bit out of line. My teeth don't feel like they just fit into each other like normal and I have to slide my mouth about until it feels natural. Could this be the cause? And if so what should I do?
Thanks xx

Edit: before a few months ago it was fine, since then it was on and off but the past week it has been constant (when i open my mouth/move it side to side)

You go to the doctor, who will see if there is a muscle, or bone or other issue. There can be many reasons for this, only a actual medical exam can tell what is wrong.

It is possible to have a dislocated jaw, although it usually hurts - a lot.
A nurse (IF it's this) will put a thumb on each back lower molar and push down and sideways, or a friend can.
If it's not dislocated, then it's an abscess or infection under the gumline. Very common and you see a dentist.