OPK for hpt..

So ladies for those of you asking if you can use an opk as a hpt. I'd say the answer is yes. If you don't have an hpt available to you and it does take a lot of hcg. But mine did not turn positive until after I got a positive on an hpt. Two days ago I took an hpt and opk together the opk was negative they hpt was positive. Today I took an hpt and opk together and they were both positive. I'm 13 Dpo. It's one day before my expected period.