Positive opk but negative hpt but i am 11 days late for my period and ovulated at the begining of the month how is this possible?

Repeat preg test: Pregnancy test kits are not 100% accurate. You can try a different brand to definitively rule out pregnancy. Another possibility is that you ovulated weakly and did not produce enough progesterone to have a menses. Also, some women have chronically high LH levels (PCOS) so the OPK show positive all the time or erratic results. If you have a history of irregular menses then that is more likely.