Starting fertility testing, advice?

Hi Ladies, I'm starting fertility testing in January and wanted some advice. I've been TTC for a year and have had 2 miscarriages. We're going to get blood work done for chromosomal testing and either the saline ultrasound or HSG. Since we have gotten pregnant on our own, just not successfully carried, my doctor mentioned the saline ultrasound. Doing a little research, I'm wondering if I shouldn't ask for the HSG instead. It took about 6 months each time to get pregnant and I'm wondering if one tube might be blocked. Any advice or anyone who has been in a similar situation?