I need to run a lot, but my legs just can't take it. At school I have to run Monday, Tuesday and Thursday. I feel great on Monday and I run fast. Tuesday I feel pretty good, but I have to go a little slower because my legs are just sore or hurting. By Thursday I go pretty slow because my legs feel like shit. Then by the time Monday comes around I feel good and that cycle starts over. Over the summer I've been trying to build up my strength in my legs but they are not getting any better. I tried getting good running shoes and it didn't work. Any suggestions?