In Act 1, there is considerable proof that Romeo is obsessive, and therefore, not objective about love. His mooning over his lost love, Rosalind, is more than his friend Mercutio can bear. In flowery language, Romeo opines:
She hath, and in that sparing makes huge waste.
For beauty starv'd with her severity
Cuts beauty off from posterity.
She is too fair, too wise, too wisely fair,
To merit bliss by making me despair.
She hath forsworn love, and in that vow
Do I live dead, that live to tell it now" (1.1.216-223).
Mercutio will have none of it. His advice? "Examine other beauties" (1.1.226).
Romeo rejects Mercutio's directive, but then immediately falls in love with Juliet the second he sees her at the Capulet ball. Despite all the obstacles before them, Romeo continues with his unrealistic love, even dramatically sacrificing his life...and obsession if there ever was one. In language that makes his obsession with Rosalind sound reasonable, Romeo dramatically drinks from the poison vial, saying:
"...Eyes, look your last.
Arms, take your last embrace! And lips, O you
The doors of breath, seal with a righteous kiss
A dateless bargain to engrossed Death.
Come, bitter conduct, come, unsavoury guide,
O true apothecary,
Thy drugs are quick. Thus with a kiss I die (5.3.112-120).
there doesnt have to be proof its what he feels you just have to believe it
romeo is often seen as a player, switching crushes so quickly, some say this shows his lack of true love, others say it shows his foolishness and some, how much he is truly attracted and needed to be with juliet. take your choice, it is all down to interpretation in the end!