Hello
If you ovulated on Sept 17 and you suspect you may have conceived you should be able to take a HPT by now to see if you are pregnant.
Our bodies and cycles can change at any time for any reason: stress, illness, just because, especially as we mature (dont like saying "get older" LOL)
I had an unusual cycle last month and went to the dr and they found my left ovary full of cysts. I do have PCOS which I manage by diet but wasn't expecting it to be so bad, but I wasn't shocked either. The cysts are what threw my cycle off.
Not suggesting you have cysts, just better to go the dr if you still have a concern next cycle and want the best answer. Especially if you are TTC
Sorry I couldn't be of more help and GL!