22 weeks pregnant. Took car ride but kept stopping to stretch, now I have top of knee pain only when I walk or knee is bended. Can this be DVT?

No. DVT doesn't cause knee pain, it causes swelling of the involved leg predominantly. When pain is present, it tends to be in the calf.
Possibly. If pain is severe, swollen and hard to walk best to see your doctor or go to an emergency room to rule out blood clot.