When you can swing it, or if insurance will cover, I definitely recommend getting hormones tested regardless. Progesterone, estrogen, testosterone, and estradiol. I think there's another that's actually a thyroid thing, but 3-4 months after you quit birth control, things should be close to "normal" so it's a good time to test if your cycle is not regular at that point.
I was on birth control pills for about 5 years, trying different ones periodically when one would give odd side effects, before I finally gave up on them. I had never had a sex drive for very long, probably thanks to depression, SSRI's, and then hormonal imbalance, and I wanted to see if it would improve. It was not for another year after that I got my hormones tested, found my progesterone to be low, started supplementing Vitex, and noticed improvement. TL;DR, not related to mood exactly, but it was important to me and definitely makes me happier .
Do you feel like the fish oil makes a difference? I'd heard it's good for depression for YEARS and it never did anything for me.