my sad hip flexor

i think my left hip flexor is strained, it hurts to lift my left leg and the pain isn't coming from the quad area. its been hurting me for a couple of weeks now and I thought it was just tight so I've been trying to stretch it but i realize now I have to work on strengthening it.. but it huuurrtss! i did some core exercises tonight but wasn't feeling the greatest. I felt sad & i'm not sure why. tomorrow I wake up to run, so I'm going to bed now. nite nite