Am I being unreasonable?

My boyfriend moved in with me almost a year ago. We had a few bumps along the way but things have been good overall. He has been fairly good at paying his share of the bills however he still owes me money for August and September. Today I found out he paid $600 for an acting class for his 14 year old daughter who he admits shows him little respect and refuses to go to school on a regular basis. This upsets me and makes me feel taken advantage of. Am I being unreasonable?