aching type pain on my right leg in the knee area

Having a aching type pain on my right leg in the knee area. it starts at what seems to be the head of my fibia, about half an inch below/right of my knee cap and the pain continues over to the right side of my knee and then at the back of my knee. at certian times if i apply hard preasure to the right side of my knee where some of the pain is it will "transfer" some of the pain to a spot right under my knee cap. as far as mobility, although i can walk just fine, the pain doesnt keep me from walking around the house/yard and such (yet anyways) i cannot bend my right leg all the way (as if i wanted to squat) because it adds preasure and it feels like something is going to "pop" out of place. weird thing about this though is if i use my thumb and apply preasure to the back of my knee where there is pain, the pain goes away when my knee bends. while im here i might as well add that sometimes i have to becareful when i climb in bed or on the floor (im slightly pegion foot) or i will feel my leg pop and when i straighten it back out it pops yet again but this time it will hurt and the right side stays sore for about 15 minutes. scares the hell out of me sometimes because i keep thinking i am dislocating my knee or something. i was told once a few years back before i started having these issues that i may have arthritus in my knees but due to my visit being about something else thats about as far as it went. i was hoping that i could get a clue to what could possibly be wrong here so i can look into it further and see what exactly is wrong before i go spend a bunch of $ on a dr. visit (no insurance) if its just something i can fix with stretches and such. hopfuly soon though because sometimes i even have trouble going to sleep. i cannot remember injuring it other then slipping in cat sh-- while walking down a hill. lol anyways, thanks!