Bad hot flashes and loss of vision

I’m 24 weeks pregnant with my first baby and a few months back I had an episode of extreme sweating with loss of vision and almost passing out. I told my doctor and she just said to eat more and stay hydrated it didn’t happen again and I was completely fine afterwards so I didn’t worry much. But now it has happened twice in a row this morning and lasted longer than last time I also ate to see if i would make me feel better but I still feel faint and just terrible like it’s going to happen again. My doctor told me to eat more again and that’s all should I get a second opinion or trust her?