Foam rolling thighs causing hematomas below knees?

Hi,

I´ve started foam rolling to alleviate my tight thighs, and knee syptoms that seem to have generated because of the other thighs worse tightness. I think I´ve managed to roll with a decent technique for a couple of weeks now, and noticed relief in my thighs and the problematic knee.
At first it was hard for me too keep a good posture, and so I had too much weight especially on my outer thighs. And this, inevitably, caused some small bruising on my outer thighs. But now, although gaining a better technique, there seems to have occurred another problem. After the evening that I´ve done the rolling, (and only on my thighs, not calves!), the next day I´ve noticed a hematoma on the side of my shin, below the knee. This has now happened once on my both shins. And I believe there´s a correlation between rolling and those hematomas. Hematomas have been smallish, approximately 2 inches of diameter, with a noticable colored bruise, a bit swelling inside, and some soreness when touching or put weight onto. I´ve had some rest with these for some 24 hours, kept the leg up and held ice bag on the hematoma. This seems to have helped. But it´s not nice at all, because I think that foam rolling would be a real relief for my thighs and knee though.

So I´m a bit worried what could be the issue, maybe having some problem with my lymfatic system, or weak blood vessels. Should I stop rolling completely.... My sports are just walking, cycling and tai chi. I´ve had blood test panels quite recently with no signs of blood-type disease. My only medication is a smallish dose of l-thyroxin for my not-so-severe hypothyroidism. I take vitamins in cycles with pausing periods: vitamins d and c, b-complex, moderate dose of omega-3(fish oil), zinc, copper, magnesium I take almost everyday with a small extra calcium.

So thankful if anyone has any opinions about his case!