The short fuse / irritability are definitely signs of overtraining. Not specially what this post was about - general signs of overtraining have been talked about on previous podcasts (pretty sure there’s a recent one with overtraining in the title) i’d suggest having a listen to that and seeing if you’re suffering any other signs.
Fainting in itself can just happen if you have low blood pressure (which seems to go hand in hand with being fit)
There definitely seems to be an art in reading the signs and knowing when to push through and when to have a rest!