Achilles Problems

I have a constant dull ache in the back of my foot where my achillies tendon is. I can’t remember when the problem actually started but it has definately been going on for 3 months+ and has recently seemed to get worse. My ankle is especially bad first thing in the morning but if I walk for any distance at anytime it starts to ache. I went to see my doctor and he told me it was caused by wearing high heeled shoes but I’ve stopped wearing the really high ones and the problem hssn’t gone away, if anything it is worse when I wear flat shoes. Has anyone else had this problem and if so, what did you do to solve it?