Perhaps try to reduce stress?

I will let the competent individuals give better advice for the rest. But I know that from my eternal 120 I dropped to 115 - and it SHOWED, especially in my face, which scared my mom - when I started my Ph.D., which happened to be after my first intense summer of cycling. I was really stressing my body and mind quite hard that September. Reducing stress, and making sure I filled my caloric needs with many healthy meals (more like 5-6 than 3) seems to have fixed that...