Is regret a part of the grieving process?

Because the more I read about drug-induced autoimmune conditions (known about since the 1940s!), not only do I cry and curse a bit more, I also have a deep, abiding regret - because had I been better informed before I took certain psychiatric medications (for over 10 years), and that one antibiotic I had a severe allergic reaction to in 2009, I'd've most likely opted to NOT take any of those medications at all!

Dammit!