But I don't think one can control what one feels, not be free of feelings so easily.

Hm. I think that I have not spoken about something to be able to control ones feelings. You can't. That much shall be obvious. Once you feel jealousy or anger or sadness or joy, you feel it despite whatever relationship you're in. In fact, if one could not feel, then marriage would be obsolete, any relationship would be senseless.
A mature person accepts the emotions under which he comes and tries to live artfully through them. One form is the art of marriage. In other relationships, like for example between male comrades, it needs another form of handling. And so on. Marriage would be no training ground for lovers if feelings weren't there.

Do you believe that every love relationship should end in marriage?

If it is love, it is or will become marriage. Just because there is the official act (it is meant to be something for people on the whole to see that there are millions of married couples by a common form of language/symbolic acts, like in Christianity and other religions) it does not mean that you don't feel married already (by the acceptance of living out the highest ideal between man and woman).

So for me, marriage is the result of wanting to love fully.
To answer more concrete: No, not every relationship which one thought of it being love, need to end in marriage. There is an engagement period of several months, it can also last longer (but preferably not several years, that would break the rule), during which the opportunity should arise and be sought to get to know each other well. If it's still love after six or so months, then why not marrying?

My man married me before I married him ;)