You may be interested in these previous discussions of the same question:

https://www.reddit.com/r/AskHistorians/comments/2ufje7/what_would_have_been_muhammads_religion_before_he/ https://www.reddit.com/r/AskHistorians/comments/28n21d/ama_preislamic_arabia/cici0qv

as /u/riskbreaker2987 noted one of the biggest problems with answering this is the lack of reliable documentary sources to support the traditional narrative of the religious sources.