Hybrid injectors experience?

Jessica
34, TTC #1 for 2 years. Been on several rounds of Letrozole and had one unsuccessful <a href="https://glowing.com/glow-fertility-program">IUI</a>.  Becoming increasingly frustrated and depressed about it not happening. 
In the past I have always produced 3 nice sized follicles, but last time just one. Dr suggested hybrid injectibles, which would cost another $600 on top of the $800 for medications and <a href="https://glowing.com/glow-fertility-program">IUI</a>. I just don't understand why they would suggest this when I've had great responses to the Letrozole producing follicles before except for one month. 
Has anyone had experience with injectibles? How much more does it increase your chances?
Also any advice on how to keep your head up through all of this would be appreciated. I'm getting emotionally worn out.