The relationship between Hamlet and Ophelia being as unclear as it is, there are two points where there is no doubt:
1.Hamlet did at some time love Ophelia sincerely.
2.When at her grave he cries:
I loved Ophelia; forty thousand brothers
Could not with all their quantity of love,
Make up my sum,
He must have spoken sincerely. Furthermore we may take for granted that he uses past tense because she is dead and not because he no longer loves her.
This brings us to the most popular view of their relationship. According to this view, Hamlet's love for Ophelia had never changed: he only felt his duty to his dead father was more important and he put his love aside. In addition, he felt obliged to make her believe that he's mad so as to make others believe it too. This was the purpose of his crazed-lover behavior in her chamber.
Also he might have entertained faint hope that he could share his secret with her, but the study of her facial expression must have dispelled his hope. In the Nunnery scene he addressed her in bitter and insulting language so as to make her believe that his love for her is utterly gone. Finally over her grave he can no longer contain himself and bursts into a declaration of love for the deceased.
Now, this theory is certainly wrong at one point and that is the claim that Hamlet only pretended his bitterness to Ophelia. Questions are raised:
a.Why doesn't he make any mention of her in her first soliloquy?
b.In the second soliloquy neither? This is the point after the departure of the Ghost where Hamlet should have mentioned his lover had he decided to put her aside in order...