I was not married in the church, but do go to mass. I cannot receive communion, can I serve on the parish council?
Diocesan and parochial Pastoral Councils and Parochial Finance Councils, of which non-ordained faithful are members, enjoy a consultative vote only and cannot in any way become deliberative structures. Only those faithful who possess the qualities prescribed by the canonical norms may be elected to such responsibilities.
Code of Canon Law:
Can. 512 §3. No one except members of the Christian faithful outstanding in firm faith, good morals, and prudence is to be designated to a pastoral council.
Catechism of the Catholic Church:
1650 Today there are numerous Catholics in many countries who have recourse to civil divorce and contract new civil unions…The Church maintains that a new union cannot be recognized as valid, if the first marriage was. If the divorced are remarried civilly, they find themselves in a situation that objectively contravenes God’s law. Consequently, they cannot receive Eucharistic communion as long as this situation persists. For the same reason, they cannot exercise certain ecclesial responsibilities…
If you are in a situation of being divorced and remarried then Church documents are pretty straightforward that individuals in that situation should not be on parish councils. If you are simply in a situation where you were married outside the Church and are eligible to have your marriage validated then that is the best course of action.