This morning when I went to the bathroom I noticed that there was light pink blood on the tissue. I've just found out that I am pregnant and am about 4 weeks. Am I having a miscarriage?

It's impossible to tell for sure based on what you've told us, but it is not uncommon to have a little pinkish loss at implantation and around the time of your missed period. This does not necessarily have any serious repurcussions. A scan at 5-6 weeks would hopefully put your mind at ease.