No period and then unusually light period pls help??

I’m 18 and usually I miss one period every 3-4 months probably like at least 3 times a year and when I have my period the rest of the time it’s pretty on schedule and I get it late sometimes but usually its heavy and dark for the first 3 days with a lot of pain in my back and legs and stomach then mid heaviness the 4-6 days after and some pain, and now last month I didn’t get it at all, and I did get it the month before that one so I thought I’d get it last month and I didn’t and now I got it around 2-3 days ago no pain which is not normal for me but it started w spotting then the past days since I’ve been having like brown blood and light bloody discharge?? And then since yesterday/last night there wasn’t really too much blood on the pad and there was like not dark blood when I wiped like usual but just SOME red/pink like not too much and now today at 8pm there was some light blood on the pad and like nothing when I wiped like it was that light brownish color when your period is ending, and I don’t know what’s going on my vitamin D is really low for the past months like I got it tested around 4 months ago and was told I should be at a 30 but I was at a 10 and I haven’t taken anything for it so maybe I’m lower now, but if that’s not what’s affecting my period then idk what it is and it’s making me worry does anyone know what else it could be?? Should I go to the doctor for this? And I am not sexually active at all and never have been so not pregnant