I started with breathing problems yesterday worse today and iv just found a lump on my inner leg a bit above the knee any advice please?

Blood clot: The main concern with a lump in the leg and breathing difficulty would be leg phlebitis with clot travelling to the lungs. This would be even more suspicious if the lump and calf are tender, in a venous area and there is leg swelling. I recommend an examination in the hospital emergency room especially in view of the breathing complaints..