Hey veganDreama,
Do try and be kind to yourself and maybe see if there's someone you can talk to, as you do seem to have lots of anxieties about weight gain and food. Coupled with your past history (of being both overweight and very underweight) this suggests you probably do need some help - maybe counselling with someone with ED experience?
Exercise is great - and, while rest days from strength training are important, there's nothing wrong with being active every day - it's good for your body and mind. But to me, the way you speak about your fear of gaining weight, and your very rigid exercise regime, suggest you probably need to find a more relaxed balance. (I try to run and work out around 4 times a week and, in the past, used to get very anxious if I missed a training session - but now I've learned to just accept it.)
A BMI of 21 is a slim, healthy weight, so you've no need to lose any more weight - and while I understand your fear of gaining, adding in a few relax/rest days to your impressive exercise schedule really won't cause that to happen.
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