Does loosing a lot of weight really mess with your period ?

I’m 21 days late, I’m very irregular so it’s confusing to ever know what is ever the reason for my period to be late. I have taken 3 pregnancy test that all came out negative ( taken at 15-18 days late ) so I’m sure I’m not pregnant and I have a feeling it’s stress and how much weight I’ve lost, I used to weigh 167 now I weigh 151, all in the time of 3 months.

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