Non-healing quad pull

Hi gals - sory this post is so long, but I feel like I need to explain what's going on and see if anybody has any other ideas on things to try.

I feel kinda silly asking this, but I'm out of ideas. March 14th when I was running 8mi (longest run this year, but I had built up to it), I had a little bit of a pain in my left quad, a little medial but not enough to be an adductor. I finished the run because it was not severe.

It felt fine for a few days afterwards through some bike rides, but the next time I attempted to run I had pretty severe pain in the same area and had to just stop. That was Mar 19th. I tried for a few days to just do some very low intensity exercise, mainly biking in a low gear, but it became worse (hurting more often with almost all activities, and some pain in other areas in my leg, probably for compensating for the injury).

So I took time off from March 24th through April 8th. I literally did no type of exercise, stretched gently, and took anti-inflammatories. By about April 3rd or 4th, it did not hurt with just regular activities, ie I could do a fast walk without pain.

So I did a couple of very easy, short bike rides. No problem. Tried to do an easy walk/run combo, with more walking than running, and it started hurting again, but not as bad as before. So I stretched and took a couple of days off, then did an easy bike ride this Wednesday. Felt great during it, so yesterday I did another walk/run combo. Felt fine during the run, stretched afterwards, but yesterday evening it was hurting again, and today I'm having actual pain just working around my house.

So my question is there anything else I should try? I'm out of ideas. I've done rest, anti-inflamatories, gentle stretching, and slowly restarting after no more pain. Let me know if you have any other ideas. I've never had a muscle injury last this long before.

Is it a quad pull, or is it a pronated foot/medially torsioned tibia/internally rotated hip?

sounds like all your activities are fine, until you get to running. Are you doing any other high-impact stuff? (jumping, jump rope, hopscotch?) Does it hurt, too?

(if you look at an anatomy picture, is your pain in the neighborhood of vastus medialis obliquus?)

It is actually exactly where my vastus medialis is. The pain actually runs in a line down my quad in that location.

My hip isn't rotating medially, if anything it rotates laterally (turn-out from ballet). My running shoes were pro fitted and from what I can tell I'm not pronating now, but I have a tendency to if not in proper shoes due to my arches collapsing. I've never noticed any type of tibial torsion, but I haven't had that checked out by any means. One problem I do have is a slight leg length discrepency, with my left leg being about 1/2cm longer.

Running is the only thing that hurts now; well, after aggravating it yesterday it is sore with pretty much anything, with occasional pain. Biking bothered it right after I injured it, but hasn't since taking a couple of weeks off. No other high impact activities, but I do horseback ride and jump quite a bit, but that has never bothered it, but that uses the adductors more than my quads.