The next step, can you help answer some questions?

Marie • Working on # 4 and happily married.
Ok so this is taking a lot longer than expected. I feel we're losing time! I'm 35 DH is 40. I had blood work and levels tested on the 3rd day of my cycle three months ago. All was in normal ranges. I've had a u/s and pelvic u/s. All normal no growth/cysts ect. I'm charting and using OPK's and still nothing! We have 3kidd currently so not sure why this isn't working. I am willing to except the it will "happen" once I know the following. 
1. My tubes aren't blocked
2. Confirmed ovulation seen on u/s or blood tests. 
3. DH gets his swimmers tested. 
So ladies how do I go about this? I emailed my dr as she said to try a few cycles and temp and OPK which we did. So hoping she referrers us somewhere so we can check the plumbing!!
If you'd be so kind to share how your experience went that would be nice of you and appreciated sincerely. 
Good luck to us all!