Not really. Só also means "alone". People prefer to use só because it is shorter =)
is there a difference in pronunciation between so in this sentence and sou when you say eu sou....?
Só has an open 'o', halfway between 'ah' and 'oh', or the first part of 'awe' before the mouth starts closing. 'Sou' has a closed 'o' going to a 'u', so it sounds more like the 'oa' in 'boat'.