Back/leg pain

Please help, I was treated for a sacro illiac strain a few years ago, that re occurs from time to time. The pain and discomfort lasts a few weeks and normally after treatment from an osteopath it goes away. I teach Spinning Classes and more so recently have started teaching Body pump.
Earlier this year i trained to power walk the marathon but started to develop problems with my hip/buttock area. I had treament from a chiropractor which eased it slightly but it never cleared completly until i stopped the training. My problem that im getting now is that my buttocks, hamstrings and now tops of my calves and outside of my knee ache almost constantly after exercise. Its not really painful and not the general ache you get after exercising but just a dull ache that last for ages after. I am even feeling these aches from general walking around. The other week i thought i had pulled my back again but after some light manipulation on my sacrum, to my surprise, i released whatever was causing the pain and it cleared almost instantly (something i have never been able to do before. Any ideas what can be causing the aches? the more i read the more confused im getting!!!!. Any advice on who i should go and see. I have started to spend more time stretching but not sure what else i can do…..