I also recently started taking lexapro a month ago. Everyone feels the effects of the medication differently. Luckily for me, it was clear that I had a chemical imbalance and the medication helped right away. The first week, I was drowsy and miserable, but I stuck it through and now I can say I feel normal. I've been having problems in my 4 year relationship as well. The medication has helped my emotions stay balanced. So for example, in a certain situation, I will react a lot more calm and rationally than when I wasn't on medication. I am a lot less bothered by silly small things. My boyfriend and I were doing very well, but now i'm having doubts again, and I don't think it has anything to do with the medication anymore...I think it's us.
In my opinion, if the medication is effective, it will assist in you getting a handle of your emotions and probably think a lot more clearly. Hope this helps