If you were validly baptised (into any christian sect) you have a god-given right to recieve the sacraments. That is tempered by the necessity to properly understand what the sacraments are.
You understood enough to receive Confession before receiving the Eucharist.
Provided you understand and accept the churches teaching that the Eucharist (Holy Communion) Is taking and eating the Real Presence of the Body, Blood, Soul and Divinity of Christ Himself then you are capable of being In Communion and are not committing any serious error.
If you have not been properly prepared by a priest or catechist then you have breached the disciplinary rules, but if you were unaware of them then you did not commit a serious sin. (One cannot commit a Mortal Sin by accident or in ignorance - no matter how Grave the offence)
You have now realise that there may be procedural matters which could render your current situation “Illicit” (against the cannon Law). to rectify this you must go and talk to your priest. He will consider your current level of understanding and tell you if you need to go to RCIA classes or come back to him or another catechist for a few personal sessions, or (hopefully) he will judge that you have sufficient understanding to continue to recieve the Euharist.
You will of course need to undertake some preparation for the Sacrament of Confirmation. Most parishes should have a programme for educating adults for this. that may be part of the RCIA programme or it may be a separate programme, or even a series of 1:1 meetings with a Priest, Deacon or Catechist.
Welcome Home.
Have no fear, but rather Hope in the Lord.