Could this be a serious illness? I'm not on anything, I haven't changed my diet, or my lifestyle in anyway; but, recently, I've felt a tightness in my heart, pain in my stomach, weakness, dizziness, blurry vision, sudden cold spells, terrible balance & walking wobbly, increased pain in the left eye---among other common things. Almost like a cold or flu, but without that groggy, foggy, fever-ish feeling.

These things came suddenly when I woke up only three or so days ago. I'm a healthy 15 year old not involved with drugs or anything remotely close. I'm active and such---I would like very much to avoid going to a doctor so as not to worry anyone; but, I really would like to know what the things above could mean or lead to. Thanks a lot!

Summarized question: What is the diagnosis for symptoms like tightness in my heart, pain in my stomach, weakness, dizziness, blurry vision, sudden cold spells, terrible balance & walking wobbly, increased pain in the left eye?