Medications : Clomid, letrzole, etc. ?

First time posting in this group. I am sorry if this is not appropriate to ask. But ... Would someone be willing to help me understand the different medications?

I had an ultrasound the other day to reveal immature follicles and based on where I am in my cycle they should not have been that small.

So, without talking with my doctor yet because we are waiting on cycle day 20 labs...

I’m guessing I would need ovulation stimulation to get the follicle size larger? I show ovulation with bbt and we did have a bfp in July but then it ended in a chemical.

They did say we could be referred to a specialist, then do hsg and semen. But I’m very curious about the medicine at this point.