The fertility specialist, known as a reproductive endocrinologist (RE), will do day 3 (of your cycle, i.e. day 1 is your period) labs. They will likely also have you do a HSG test, which is short for a long-worded test that essentially checks to see if your tubes are blocked (in my case it showed that one of mine was blocked).
Your husband should also have a semen analysis to rule out any male factor infertility (MFI). There may be issues discovered with one or both of you in terms of your fertility, and this is important to know.
This information will be used to help get an idea of what your diagnosis is, so you can decide how aggressively to pursue treatment. In my case, due to my age and dx, we went straight to IVF.