Tangents symptoms and conditions

I feel somewhat reassured that it's a possibility that my memory loss is a side effect of lamictal. I was diagnosed with BP I and the medication has done wonders. I still get very depressed sometimes, but not as severe as it was without the med. I experience(d) rapid-cycling which I was told is less common for this disorder.
My short-term memory is horrible. Sometimes have trouble remembering conversations and even things that happened a short time ago. For example, I recently played a few games of pool with my son and on our way home, I couldn't recall whether or not I won any of the 3 games. It's pretty embarrassing and scary when someone "catches" you or notices that you have completely blanked. I have to write things down if I want to discuss them with my therapist, because I won't remember what my issues were within the last week or two. Sometimes, when someone asks me if I remember something, I act like I do, because I probably should remember it. Again, I feel like an idiot because I don't. At work, it's not too much of a problem, because I insist that everyone sends me a reminder email, so I have a task list to work from instead of recalling things from memory. I also get completely lost in my train of thought during conversations. I tend to go off in tangents and completely forget what point I was trying to make.
I also have trouble focusing and my mind is always because obsessing over some thought, usually something negative. I feel like I waste a lot of time doing unproductive thinking. I'm not sure if this is a symptom of the disorder of not.