I Miscarried 3 Times.Can I Conceived Easily

I am 36 years old.I got married in Nov2005.I miscarried 3 times (May2006,August2006 and May2007. Everytime foetus didnt get heartbeat and DandC was done all the three times around 8 weeks of pregnancy.After third miscarriage,my doctor advised LIT and it was done 15 times till Oct.2007.Since then I have not conceived. We tried one attempt of IVF in Nov2008.Three embryos were transferred but I dint get pregnant and the doctor told that the reason of IVF failure could be fragmented embryo.Anyhow, now I am on Hyponidd(2 tablets each with breakfast and dinner), Loprin-75(1 tablet a day) and Sysfol(1 tablet) to cure harmonal imbalance which may be causing temporary infertility acc. to my doctor. Also, I take 1 Thyrox-50 everyday because thyroid was detected 1 year back but it has been normal after taking thyrox.My husband's semen count and motility is good according to reports. He is 44 years old. We dont have any kid till now. We have undergone uncountable tests from time to time prescribed by highly reputed and experienced doctors and we have strictly followed their advice and treatment everytime. All this cost very high yet it has not yielded any positive result and we are totally emotionally drained out.My HSG is normal and follicular study is also normal.What could be the possible reason of not conceiving for the last more than 18 months? Is there any need of IVF at all in my case as I conceived easily and naturally 3 times?