Can I be a muslim and a christian at the same time?

So as I understand it, to be a muslim you have to believe that there is no God but God/Allah and Mohammed is his prophet. As a christian, I already believe there is no God but God/Allah, so that's part one sorted, and if I believe that as well as Jesus Christ being the son of God, he also sent Mohammed to convert the people further east to his word, does that mean that I am muslim as well?