After waking to go to my baby i blacked out, fell down, and limbs began to shake uncontrollably. low blood pressure or seizure? has happened before.

Sounds like seizure : This sounds like you may have had a seizure with the shaking and blacking out. If this is happened to you before, you definitely need to follow up with your primary doctor for further evaluation.

Need more info.: Syncope from low BP can be accompanied by seizure like movements which can be mistaken for a true seizure. They are thought to be related to transient hypoxia.With this type of "convulsive syncope" the seizures are relatively brief as compared to epilepsy.One clue: IF YOU HAD A WARNING prior to passing out, i.e., feeling faint and/or vision going dim or black then the cause was low blood pressure.