I was referred after six months because of both irregularity and painfulness of periods. I eventually received two diagnoses - endometriosis and PCOS. Endometriosis was the overall cause of my very painful periods (my problems with this disease started at 14) and PCOS caused the irregularity of same.
I would put money on it that you were put on the pill at 15 primarily because of painful periods which was caused by endometriosis; this dampens down the endo but it does not go away. When you ceased contraception it unsurprisingly came back.
Unfortunately endometriosis is very much underdiagnosed and it can go unrecognised. You now need proper investigation by a gynae (GPs are not always up to speed or have enough expertise in such matters) and you need to be now also determined in order to get answers. The causes of these need to be addressed.
Would suggest that you start keeping a daily pain and symptom diary as this will also give the gynae clues.
I had implant removed last August and up until December my periods were very irregular but the last 2 cycles have been 27 and 28 days! I've always had painful periods and I've been on the pill since I was 15 as my periods were so painful.... So will most GPs not really do any investigations until ttc for 12 months?
How long have you been trying to conceive for?. If its a year or nearly that I would pay a visit now to the GP initially.
OPKs can give misleading results so should really not be used.
What are your periods like generally in terms of both regularity and pain?. If your periods are always very painful and or irregular in nature the causes of these should be properly investigated by a gynae.