What everyone has told you so far is correct - and you need to answer a few questions.
In sum, if your original marriage to this man was a Catholic one, and neither of you obtained a decree of nullity for that marriage, then you have never been “unmarried” to your “childhood sweetheart”, regardless of the number of marriages you contracted in the interim.
To receive communion, you would obviously need to go to Confession and ask forgiveness for having lived with and been intimate with (I assume) other(s) since your civil divorce and now.
The WORST situation you could be in is if either of you remarried in a Catholic wedding and neither of you obtained a decree of nullity for your first marriage. THEN, you would have some serious problems to deal with.