Meg , know exactly where you are coming from , last year I felt like you do now ,you MUST go to your GP tell him about your probs , he should give you a blodd test that will measure the inflamation in your blood, check your thirio and calcium levels and all sorts of other things.The results take about 3/4 days then go back and see what they were. If its Osteo Arth. your levels will be normal and he should prescribe painkillersand physio and maybe something to help you sleep like amatryptaline (sorry sprlling not my best subject).If the levels of you crt are high you will be refered to a rheumi and he will pinpoint the type of arthritis you have and start a course of treatment. The longer you leave it with out treatment the more distorted and painful they will become. Your gp wont have a go at you for being overweight -mine never have and like you I am about 2 stone overweight. Get it under control then promise yourself you will cut iut your bad eating habbits.
Good luck I really feal for you.