At 15.5 you need to know that married couples want to have sex with one another; it goes with the whole wanting to marry one another deal.
If one does and the other doesn’t want to have sex and potentially have children, they have got serious marriage problems. The Church endeavors to prevent serious marriage problems and writes its rules accordingly about marriage to try to prevent serious marriage problems. The rules are written for average normally healthy people.
If one spouse or the other has got serious health problems and it is of grave concern not to have children, of course they do not have to have sex.
If you are not married and you have got serious health problems and it is of grave concern not to have children,* anybody who would sign up to marry you must very fully understand and accept all of that and live with that every day 24/7 as a permanent condition. The Church has to seriously evaluate such situations and your mutual consent and overwhelming commitment to one another in light of that situation in order to bless your marriage. It is an individual case-by-case matter beyond the standard rules.*
As for the question of loving someone, according to Christ, we are supposed to love one another and that means everybody on the face of the earth including our enemies. Loving somebody, even very intensely personally loving somebody and feeling sexual feelings toward somebody does not mean that you marry and try to have children with them or otherwise have sex with them. Marriage and endeavoring to have children with someone, having sex with someone, is an entirely separate and extremely specific case of loving somebody.