I know its hard pretending all the time and you shouldn't have too! You deserve to be happy and not exhausted like you are. It sucks that these feelings come out of the blue with no apparent cause. I hope you are able to find the energy/willpower to call the doctor. My thoughts and prayers go out to you!
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"If love was a raindrop, i'd send you a shower. If a hug was a second, I’d send you an hour. If a smile was water I’d send you the sea. If you needed a friend, I’d send you me"