I am so sorry that you are feeling down, I know what it feels like when a medicine lets you down. I was on Lamictal in the past and it made me feel good/alive for about 8-9 months before the bad depression returned.
My pdoc added another mood stabilizer which helped a lot. It wasn't perfect but it was better than what I have been feeling. I was also put on an anti depressant for a short time.
Zomese you are still on a low dose, so I would give it some time to kick in. On average it takes 2-6 weeks before the full benefit of a med can be felt.
Best wishes to both of you!