My 10 y.o. dog is acting strange as if scared of something

My 10 y.o. pitbull has been acting very wierd for a few months now. My husband and I will be in the living room and she will be laying and the floor and out of the blue she will just jump up and start doing laps around the house....or if she is just standing still she will bug out where she is standing. When she does this her ears go back and her tail is tucked between her legs and she shakes uncontrollably and breaths very heavy as if she is not getting enough air but as soon as she is relaxed again...it goes away and then will happen again. It happens throughout the entire day. When it comes to going to bed at night she will lay down for a while then get up breathing so loud that it wakes me up and she just shakes and shakes and sometimes even jumps up on the bed trying to get on top of me...(it's very odd)when she does jump up sometimes I let her stay and try to get comfortable and calm but she will just sit back up shaking and breathing heavily and if I try to push her off the bed she literally fights mje to stay. Then she will just pace back and forth til she tires herself out sometimes she even jumps in and out of the bathtub a few times a night. I can't get any sleep and it's affecting me. We took her to the vet and was told that everything seemed fine excpet for a minor count on her unrinalysis pertaining to her thyroid which we need to go for the 2nd thyroid test. Please let me know if you have heard of anything similar to this before ...PLEASE