Delayed ejaculation?

My husband and I have been TTC 4+ years. He has always had an issue with delayed ejaculation, not being able to inside me, just with a vibrator. We've tried him getting almost there and getting on top of me or me on top of him just as he ejactulates. We also tried once with him ejactulating in a cup and putting it in me with a cough syrup syringe. Any advice or other ways to try? Getting desperate here ...