What could be the cause?

Hey Ladies, I'm 21 years old in a 5+ year relationship. We would be fine with either outcome but can not find anything similar to my situation on Google. Any advice/comment would be appreciated!

So I've been on the Pill for over a year but prior to that I was on implants and IUDs. I enjoy the side effects of the pill so much better than the ladder. We just moved 2 months ago and I began the KETO diet a month ago. Approximately around my ovulation I noticed clear, stringy mucus (fertile mucus I'm assuming) and VERY light spotting. Figured it was the change of diet. Two weeks later my period was due and I was 4 days late. I noticed "PMS" symptoms -- exhausted, moody, emotional, tender breasts, food/smell sensitivity. (I know they are similar to early pregnancy symptoms) so I took a test to be safe. Negative. An hour later, brown discharge accompanied with stringy clear mucus happened. That lasted about a day or two then period blood (medium flow) with that same stringy mucus. I've been on this weird period for almost a week when my birth control periods are normally 3-4 days (medium flow). Now it's becoming lighter. Should I take another test? If so, when?

Thanks for your time!!