Stuttering/slurring speech= Social anxiety?

This has happened for a couple years now, but only at this point it is REALLY making me insecure. When I talk to anyone other than my family or closest two friends, I sound like a babbling idiot. I can’t make eye contact for long, I start to stutter and my words even slur, resulting in a chain of continuous words with no syllables. It frustrates me to the point of crying at night and I can’t deal with it anymore. Even when I get up to present in front of the class, my head (yes, my head) starts to tremble vigorously. I can’t even walk in the school parking lot without being completely awkward and continuously moving my hands and diverting my eyes from other people. But the weird thing is, my confidence has highs and lows. Most days I’m like the description above- but on rare occasions I suddenly have this bout of self-confidence in which I feel indestructible and actually hold my head up high (but that only lasts for a couple hours). My Fluther friends, won’t you help me? Is this Social Anxiety most likely? What can be done to treat it?