Meds change leads to some horrible days

During my recent first appointment with my new psychiatrist, we decided to increase my Lamictal dosage. I was on a very low dosage and I was having some increasingly significant mood swings. The dosage was doubled, to be increased in two steps. After the first step in the increase, after about 3 or 4 days, I had a really down day. I have had, routinely, down days with increasing frequency, since ending my ECT treatments. But this one was different. It was a plunge. Very dark outlook, isolated...just a shitty day altogether. And the next day I was fine. I didn't think much of it other than it was a more severe mood swing than had been the norm.

A week later, I increased the Lamictal again. 3 or 4 days later, another (and even worse) plunge. I cried all day, thought about suicide, even worked on my suicide letter to my family. And the next day...I was fine. I don't believe much in coincidence. Has anyone else had a similar experience when increasing mood stabilizers?