Cheryl:
Roots Ireland www.rootsireland.ie has two baptismal records in Co. Tyrone in your time frame. There is one in 1839 and one in 1840. If you have his parents names, you should be able to tell if one of the records is your Robert.
Roots is a pay site to view the transcription of a church record. You can work with the indexes for free to try to confirm if one of these records is correct.
Roger McDonnell