Just because Paul says that we are not under the Law implies that we do not keep the Law. Paul is very upfront about keeping the Law and the role of the Law.
Romans 2:12-13 ASV
(12) For as many as have sinned without law shall also perish without the law: and as many as have sinned under the law shall be judged by the law;
(13) for not the hearers of the law are just before God, but the doers of the law shall be justified:
James 2:10 ASV
(10) For whosoever shall keep the whole law, and yet stumble in one point, he is become guilty of all.
Romans 7:7 ASV
(7) What shall we say then? Is the law sin? God forbid. Howbeit, I had not known sin, except through the law: for I had not known coveting, except the law had said, Thou shalt not covet:
James 2:10 also implies that the Law is still in force by declaring that if we do all the Law but miss one law in it, we are guilty of all the Law. A guilty believer cannot be saved. A doer of the Law can be saved, according to Romans 2:12-13.
Be aware of the fact that, if we do not KNOW the Law and do something that the Law forbids or do not do something that the Law requires, our ignorance will not save us but that we will perish anyway.
Hence, we are to repent and start keeping the Sabbath because Jesus did not make any declaration which annuls the observance of the Sabbath.
When you hear your spiritual leader giving you some reasoning and not a verse which unambiguously annuls or approves a doctrine of the Old Testament, know that you are listening to the voice of Satan who deceived Eve by the same false reasoning blueprint to act contrary to what God (Jesus) says.
As Paul would say, I had not known breaking the Sabbath commandment, except the law had said, Remember the Sabbath day to keep it holy.