Good question, however the information you provided is not sufficient. Without getting into more personal aspects of your own case, I’ll give general replies.
First the Church is interested in the salvation of souls, so the rules about reception of communion and who can and cannot marry (valid sacramental marriage) are in order to direct or guide us to follow God’s laws. I’m going to assume that you are planning to marry in the Catholic Church, so this reply would be applicable to someone who wants their marriage to be a good Catholic marriage, where both parties will practice their faith.
If you are not married yet, and you are in a state of grace, (not in a state of mortal sin) then you can receive communion.
As to your fianc?©e, he should speak to the pastor of your or his parish. There may be a reason why his first marriage was not a valid sacramental marriage. These could reasons could be that he married outside of the Church, at a Justice of the Peace, or at a non-Catholic service. He could have entered into the marriage because he felt forced to marry her, or if he did it on a whim, such as if he was our with friends drinking or otherwise could not form the proper intention. Did either of them in his first attempt at marriage go into the marriage with a plan to use artificial conception, and avoid getting pregnant, even for a period of time? (This list is not exhaustive)
Once again, dragging out the personal details here is not my intent, that can be discussed with the parish priest. His intention in asking the above and other questions will be to see if there is a reason to seek a declaration of nullity, (annulment) which states that there was a reason why the marriage never took place (as a sacrament).