Help I'm 16 10 weeks pregnant I staerted bleeding today like small clots now lighter earlier in day. It hurts

Since it is tapering off, it's likely from the exertion from the exercise. You might try either cutting back, or try an alternative ab exercise (which would be the recommendation soon anyway as you get farther along). Planks would be a good option and they tend to be better anyway.

If bleeding and cramping were to continue, notify your doctor or midwife.