I Am Scared of Relationships

As being single for the most of my entire life, I really don't know what to do when it comes to having a relationship with someone and trying to stop thinking of someone at the same time doesn't help. The obvious question for me is, How can I convince myself to tell this person I care for them.I have only known her for a year but I feel stuck and trapped. When ever I see her, my Heart beats faster and it's also hard to not glance at her too... If I don't do something soon,I will feel like an Idiot that doesn't have the guts anymore.Any advice?