After 6 weeks you should be able to check and not get a false positive, because by then the hCG should be cleared from your system and would no longer have been detectable
I had sex 4 weeks after my section, nothing happened. I didn’t get my first period till 8 weeks post surgery. If you have LH test strips you could test for ovulation but other than that you just have to wait. If the LH test for ovulation is negative chances are you won’t get pregnant.
It's really impossible to say when you might start ovulating again. I would use some form of protection to be safe.