What do you mean by " believe" min ? When a lot of people use that word, they are referring to trusting that something is true, without evidence. Hence they may "believe" in god.
When it comes to Science, that kind of "belief" is not necessary, Science proves what is true with satisfactory, tested, peer reviewed evidence, no " belief" is necessary.
I will not trust that something is true without the kind of evidence demanded by Science, hence I do not believe in god.
Do I believe in myself ? again, I ask, what exactly do you mean by that ? I believe I exist, I believe I can trust myself to be true to the principles I wish to live my life by etc etc. But is that what you mean ?