I had a tubal ligation been regular but last period was off lasted 2 1/2 days spotted then heavy with 2huge clots concerned could i be pregnant?

Not likely, but...: Can do a home pregnancy test if worried. A urine pregnancy test gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), 1 week after missing a period, or 1 week after starting a "weird" period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test.

Probably not but: A tubal ligation is very effective (>99%) at reducing your risks of pregnancy but does not eliminate the possibility entirely. To be safe, obtain a blood betaHCG pregnancy test which should answer your question promptly. If your pregnancy test is negative, if your symptoms persist and worry you, it would be wise and valuable to consult a gynecologist.