Go to Relate or get some other form of couples counselling. But the fact that you don't think you'll split up doesn't alter the fact that babies are not good for rocky relationships, and that rocky relationships are not good for babies.
I just read the first line of this message and my answer is NO. Only because it's a well known fact that you should not have more kids to fix a relationship. It'll just cause more problems. Try and solve your problems or split. Don't even consider more kids...remember how tired and run down you get?
My DH was a band aid baby and his mother is really cold with him compared to the love she has for his older brother because 'DH did not fix her marriage'. This was 38 years ago. I'm not saying your marriage is on the rocks, but don't add a new human being into the mix until you are happy. Relate are great.