Hey I just started Testmasters as well. My first diag was a 151...the second a 152, and I was wondering the same thing myself. Our instructor told us not to worry, as he sees very few students improve between the first and second diags, but instead that most see a jump in their scores by the time the third diag rolls around.
Oh and, to my knowledge, the LSAT isn't offered in July but rather June. Check your admission ticket on your LSAC account, they are already up there.
Keep us updated on your progress!