As mentioned below it could be haemorrhoids, but it may also just be a small tear. If you are getting constipation then a small tear can be quite common, and just needs time to heal up. It's definitely worth going to the doc for an opinion though.

A good over the counter remedy (but can also be prescribed) is peppermint oil, you can get these in capsule form. It helps settle the bowel and can help with bloating. I have irritable bowel syndrome (and go from constipation to diarrhoea, and vice versa, often), and have used these alongside my perscription drugs. The brand I use is colpermin.