Write the letter...say you're sorry. Send him the present.
You Hit First, To Avoid Getting Hurt
It sounds like you like to hit first before you get hit with any bad news. It makes you feel better to do the hurting rather than risk getting hurt.
But, now you regret it.
I think you are right, you blew it! I'm not sure he'll take you back...I'm not sure that I would. Sometimes the love is not enough. Yes, you have strong feelings for him, but you also don't trust him enough with your feelings to keep from hurting him. The trust you write about is very fragile. Getting it back means that you can make him realize that you are working on your "problem" of hurting him.
Can you stop saying things you know aren't true? Can you stop hurting to keep from getting hurt?
You have to trust yourself, really. Trust in your love, and don't worry about getting hurt. That's hard, that takes courage, and when you can do it, you'll have what you want!