Switching birth control

Okay so I currently have the implant, I'm on my second one and I'm about 2/3rd of the way through it (due to be removed April 2018). Whilst on the implant I have had no periods or cramps.. until a year ago. Now they are completely unpredictable, severely painful and I've experienced PMS that I have never had before. I can have nothing for a couple of months or two in one month! Which is really very draining (pardon the pun). I have been to the doctors several times for tests but they have found nothing. Not pregnant, no STI/STD's, no worrying precancerous looking cells (my Mum had both ovarian and cervical cancer) which was my main worry.

I was wanting your opinions if you think it's worth my swapping to a pill (I can only have progestin only due to migraines). I'm not bothered about having periods, I just want them to be more regular!! 😩 I couldn't tell you where in my cycle I am. My body is seriously messed up.

Please help me!!! ❤️