In many dioceses in the US, bishops have delegated the faculty to remit in either the internal or external forum any latae sententiae excommunication (eg. for abortion, apostacy, heresy or schism) to all their priests. The internal forum refers to within the sacrament of Penance, while the external forum takes place outside the sacrament. So if you are troubled by this, I would suggest the following steps: (1) Research the Pagella of Faculties of each diocese closest to you, either by an online search or by calling the chancery of each diocese, to determine in their priests have this faculty. (2) Make an appointment with a priest in one of these dioceses for a meeting in the rectory. First ensure that he has the faculty to remit the censure in the external forum. To avoid a lot of circular discussion, describe why you think you were excommunicated, ask him to stipulate that the excommunication did in fact occur, and to absolve you of it right then and there, using the form given in Appendix 1 of the Rite of Penance. (3) The censure will be remitted, and you will then be free to make a full sacramental confession either with him or with any priest of your choice.