Tightness in neck of womb can be one of the causes, but is rarely the sole cause for infertility
. More important, you need to investigate for the cause of missed abortion
at 22 weeks like congenital/acquired thrombophilia
profile, TSH, VDRL, Sugar level (RBS/GTT) etc.
If your tubes are confirmed (by tubal patency test) open, and you have tried 2-3 IUIs, its better to go for laparoscopy
. If tubes are open & it was your first IUI, you can go for simple dilatation of neck of womb followed by IUI.
Wish you good health.