Do pregnancy tests stop working after you're a certain amount of weeks?

Oh sweetie, that stick is flooded. That means it is invalid as the urine escaped over the max line Sorry. You might have to try again xxxx

If the OPK was positive because of high levels of HCG (HCG is a very similar molecule to LH, the chemical that an OPK measures), I'd really expect the levels of HCG in your urine to be sufficiently high to show up on a pregnancy test.

Do let us know how you get on.

With the OPK thing, you can get positive OPKs at various different points in your cycle, so no, it is unlikely to mean you are pregnant.
It is just that usually, we stop testing with OPKs after the 'first' time of getting it-usually around ovulation. We can also get positive OPKs just before AF arrives, for example.
If anything, based on this post and your previous ones, you may have been experiencing an annovulatory cycle hence the length, and you might be about to ovulate, hence the hard sensation above your pubic bone. You have also been under a lot of stress with your relationship (poor thing) so this is likely to be causing your lack of AF.

You may have read some people will get positive OPKs when they are pregnant, but you would also have to get strong positives on a home pregnancy test as well, for this to be true, sorry.

I hope you get the answers you want at your GP tomorrow.

I heard that an opk can pick up if you are pregnant but I don't know how accurate that is.

I'm a biochemist, of course I believe in the hook effect, but we see it very, very, very rarely. I think you need to see a doctor for a proper assessment.

As willitbe has nicely explained, the whole "HCG levels are too low in late pregnancy to cause a BFP" is a myth.

Very, very rarely, you can get a BFN and still be pregnant either because of the way your body processes HCG or because of the 'hook effect'.

Urinary pregnancy tests tend to show up as positive at levels of HCG greater than 10-25mIU/mL (depending on the make). As you can see on the table in the Wikipedia article, even at term, you'd expect HCG levels of 3,640 – 117,000mIU/mL, with the peak HCG levels happening at around 9-12 weeks. the point at which the hook effect is most likely as levels can be so very high.

Yes it is called the "hook effect", where the levels of hcg are so high that then effectively overload the test and it gives a false negative. It can occur as soon as around 8 weeks pregnant, but is unusual.

Diluting the urine, will produce a positive test if this is the case. I believe that it is a dilution of around 10:1 that can do the trick.

It is also (although very rare) possible to be pregnant with a negative test due to your body not metabolising the hcg into your urine in the normal way, which again would give you a false negative.

As you have already been advised, go to your GP, your gp will feel your stomach and be able to tell if your uterus is enlarged, and then be able to send you for a scan if necessary. I hope you get an appointment soon to find out if you are pregnant or not.

I took a pregnancy test 5 days overdue my due date. Very positive. I did the test to see if it would show negative. So for me it wasn't true! And I like doing pregnancy tests for experimental purposes.

In the nicest possible way OP, the only way you'll get a definitive answer whether you're pregnant or not is by going to see your GP and getting a blood test as other people have suggested on your other threads. No matter how many different threads you start on this topic, the outcome will be the same. So just make an appointment on Monday and then you'll know for sure. Good luck anyway!