Assuming this is a standard transmission. You did not mention if the clutch would disengage the transmission so you could 'coast' while in gear. If not, then you may have a clutch problem. I believe it is a hydraulic clutch. Check your fluid level on the clutch master Cylinder which should be on the firewall just above the steering column in the engine compartment. If it is low use brake fluid to fill. You should be able to see the clutch lever actuate the clutch if you look under the vehicle with a light and have someone push the clutch pedel down. If you are typically aggresive and violent when you shift your transmission you may just need a new transmission for a $1,000 or so.