Now I’m starting by assuming that you are Catholic, although your profile doesn’t indicate as such. Whole different ballgame if you aren’t.
Your situation, as you seem to be aware, is covered in canon law - par 1300ff. Desecrating the Eucharist does indeed incur excommunication. This is, in your case, of the type called latae sententiae - automatic rather than via a formal pronouncement of excommunication.
Sounds like you know that you need to seek absolution, as you say in order for the excommunication lifted. This means simply that you have to confess your sin to a priest at the next available opportunity, if you weren’t already aware of the mechanics involved. Have you ever been to confession before? There’s lots of information on the internet that can take you step by step through the process.
Normally no other or further action is required, and the excommunication is automatically lifted upon the priest absolving you of your sin. If any further action is needed, the priest himself will inform you of what is necessary to be done.
Are you confused about what contrition actually means perhaps? It sounds like this may be the heart of your difficulty. Contrition is really much more an act of the mind and the will rather than an emotion. Feelings are notoriously unreliable guides in such matters.
In terms of the sacrament of Reconciliation, you mainly need a conscious awareness that what you have done was wrong, since it offended Christ whose body and blood the Eucharist is, and an intention never to repeat the offence. Whether or how much you emotionally feel sorry for it is less important. Although it may be something you wish to discuss with the priest at confession, just for your own reassurance and peace of mind.
Hope this helps.