When you tell someone "I Love You", they should carry the weight to show that someone that you really do love them and not simply by what you feel at that moment. When you say it, make sure you mean it and ready to part anything of you for that special person. That include time, paitence, concern, understanding, considerate and many more.
Always put yourself in that someone's shoes rather than impose your own expectations and attempt to control them, try to understand how they feel, who they are and what are they driving at. Realise how they could also love you back just the way you wish to.
Love can be unconditional. If you cannot love another person without wanting to get the same return favors, then it is not love at all, it is merely just like an investment for yourself in love and relationship. If your interest is not in the other person's well being and life in particular, then it is not unconditional.
If you have no paitence and time to build that someone's life or allowing that person to be themselves and accepting them as who they are, and not who you want them to be, then you are not loving them unconditionally. It has to be a free will from your heart and soul.
Expect nothing more or near contribution in return which you think you have contributed a lot. It doesn't mean you should allow someone to mistreat you. It simply means that loving someone does not always receive the same level of love you feel you have sacrifice. Love to love. Do not expect to be love back by that someone in same way you did, you may be love in many different ways which you may not realise. It's a matter of do you want to be love that way.
Love can be lost along the way. It is easy to fall in love then to get out of it. It'a like falling into a deep well without realising you don't have a way up again. Never pressure that someone to love you like the same way you do, you will only loose it along the way. Imagine you try to grab as much sand in your hand by crunching your fist hard, it will just flow out of your hand faster than you know.