My five and a half year old chiweenie was just outside and he fell over and could not stand up using any of his legs he would try and just fall over. i picked him up and brought him inside. He finally got strength in his front paws about 5 minutes later and could sit up. His legs were all bowed out. 10 minutes later he could but was very disoriented. I tried to give him a treat he came to me to get the treat but would not get it. He then threw up afterwards i tried to get him to drink water. He would only drink what i put on my finger and put up to his face. he drank milk and is now just being very lazy. He had a seizure in december and the vets ran alot of test on him and couldnt figure out what caused it. I dont think it was a seizure this time because he was not convulsing like last time. Could he have eaten a weed or something that was poisonous ? Please let me know what you think. Should i take him to the vet again? The only reason i am hesitant this time is last time they couldnt find anything wrong with him and said as long as he doesnt have multiple seizures just to document the date and time and what happend with him

Optional Information:
Type of Animal: Chiweenie
Pet's Gender: male
Pet's Age: 5.5

Already Tried:
giving him water and milk