The process of conception require the perfect health of both partner. As far as the things in you its appear to be perfect and every thing is fine.
But the male infertility
is also an important cause for this and now a days a very common cause also. So I would advice you to have a seminal test for your husband. This test will help in finding if any thing is wrong with the semen and will help in making decision regarding the cause of your problem in conceiving. For this test you have to consult some gynecologist who will refer you to the proper center where this can be done.
Thanks and take care.