Some OBs can do parts of the testing. Depending on where you live, some of the testing may not be available.
I'm a physician (i don't do OB or infertility medicine), and I'd recommend making the 4 hour trip. Specialists are specialists for a reason, they have extra education that makes a LOT of difference. It's easy to get led down the wrong path on complicated matters like fertility. While your OB is probably perfectly good at general gyn and obstetrics, he/she does not regularly deal with complex infertility. I'd start with that person, but plan on getting the referral.
Where are you in Texas? I am in Dallas.