Hip pain

So ive just started muay thai again after one year, i trained muay thai 3 years before this long break and i didnt have these problems during those three years So when i kick high or around the side of the belly of my opponent i get really bad pains on the outside of my hip. And its just super annoying, i have asked my coaches for tips to stretch but it dosent seem to help. Anobody who have been in the same situation as me who can give me some tips and tricks?(sorry for bad english im from sweden)