When to call it quits?

Annie • 23 years old. Diagnosed with PCOS & hypothyroidism. Married for 5 years. Ellie Rose 💕👶🏼 & Millie Jean 💕🤰🏼
Month after month, negative after negative... How do you push on? 
After my laparascopic surgery revealed that everything was "normal" - even though I have PCOS and hypothyroidism - I've been asking myself how much further I'm going to go with all this. 
Fertility treatments can get REALLY expensive. Medications, doctors visits, and OPK, pregnancy tests... When do you know when to stop?