The biggest clue that you have hit a vein and injected would be the shortness of breath, heavy feeling on your chest, hard to breath, and coughing which it didn't seem like you felt too much. Just because she didn't see blood on aspirating does not necessarily mean that she didn't hit a vein. Some people don't aspirate properly. When over-aspirating (pulling back too hard on the plunger) you can collapse the vein or blood vessel creating nothing but air bubbles. You think you are good when you are really in a vein. When aspirating, you are merely supposed to "flick" back on the syringe to let a "tiny" air bubble slip up the syringe tube through the oil. If you see blood when doing this then you should pull the needle out and re-inject in a different area of the same muscle or in a different muscle. When FULLY INSIDE a vein/blood vessel, the syringe will FILL with blood. When GOING THROUGH a vein/blood vessel the syringe will bring in a couple drops of blood that will be separate from the oil (like mixing oil and water). Either way you should pull out and re-inject, you are too close and could move it a little while injecting.
In this situation, I think Tenacious D is right (+1 good post), you just had a Vasovagal Response, nerves can be a bitch and do some crazy shit man.

You had what was called a vasovagal response. Essentially it is an autonomic response to a stress trigger. Some people get it at blood draws, for example. Some are so sensitive they get it when they see blood. If you dinged a nerve or even chemically stimulated a nerve, it could cause a cascade of things that leads to a vasovagal response.

Useful to know if it ever happens, so you can avoid an ambulance bill. Lie on the floor with you legs above the level of your head and things should pass in a few minutes.

Keep in mind, as stated below, not everyone goes all the way to a faint when this happens. It is a continuum of symptoms resulting from the same autonomic nervous response.

From Wikipedia ( http://en.wikipedia.org/wiki/Vasovagal_response )

"Among people with vasovagal episodes, the episodes are typically recurrent, usually happening when the person is exposed to a specific trigger. Prior to losing consciousness, the individual frequently experiences a prodrome of symptoms such as lightheadedness, nausea, the feeling of being extremely hot (accompanied by sweating), ringing in the ears (tinnitus), uncomfortable feeling in the heart, fuzzy thoughts, a slight inability to speak/form words (sometimes combined with mild stuttering), weakness and visual disturbances such as lights seeming too bright, fuzzy or tunnel vision, and sometimes a feeling of nervousness can occur as well. These last for at least a few seconds before consciousness is lost (if it is lost), which typically happens when the person is sitting up or standing. When sufferers pass out, they fall down (unless this is impeded); and when in this position, effective blood flow to the brain is immediately restored, allowing the person to regain consciousness. Short of fainting a person may experience an almost indescribable weak and tired feeling resulting from a lack of oxygen to the brain due to a sudden drop in blood pressure."

Been on aas for about 8 years now and still have never used tren. I recently picked some up for possible use next cycle but I'm still not sure if I'm ready to ride the tren train or not. I to such as yourself started young but for awhile it was just test only cycles and I wish I would have accomplished more naturally and waited to begin aas. There's a lot of knowledge here on erpids that can be gained if you just research. Please if your going to live this life at least learn what your delts are.

TREN!...22YRS OLD... SERVES YOU RIGHT BRO,PLAY WITH BIG BOY GEAR .. EXPECT BIG BOY PROBLEMS!

same thing happened to me a few days ago, i aspirated n all and still have no idea what i was, i thought i was gonna pass out

ugh another delt horror story. Man i swear every week I read another one. I cut out delts out of my rotation for now. It seems like even when aspirating, some crazy shit happens.