Why do I have to mention Mohammed in order to become a Muslim?

ASA...I've been studying Islam and embrace the fact that Islam celebrates and does not make any distinctions between 'messengers'. Well then, why is only Mohammed's name mentioned in the Shahada? Why is his name mentioned at all? This does indeed set him apart from the other prophets. I struggle with this because I want to affirm my faith, but do not feel like this rule came from Allah......I believe it came from Mohammed himself. I believe Moses & Jesus were his messengers too! Can I just add those other names? Please advise. Shukran!