Unfortunately 勉強等しすぎて isn't natural. Tō (等) belongs to the formal style, and I don't hear it often in a day-to-day conversation. If you insist on the T sound, maybe the person is saying 勉強とかしすぎて?
Other than that, it's either 勉強のしすぎで or 勉強をしすぎて. It's perhaps useful to know that the accusative marker -o is phonetically a nasal vowel, [õ]. This is the reason I transcribe を without <w>, by the way.