Hi, Welcome to the forum. Your describe two serious problems. And everyone has given you great information about them, but I am going to say it again.
First, the inability to urinate or a feeling that you cannot urinate fully can be VERY serious. Ess, Karen and Aliveinme are correct in saying that incomplete emptying of the bladder can lead to UTIs which can cause relapses in one's MS. Also, if the problem gets severe, the urine can back up into the ureters, the tubes that carry the urine from the kidneys to the bladder and finally can back up all the way to the kidneys and cause severe damage - including renal failure.
You need to see your regular doctor and get a urinalysis to see if you have a urine infection. You need to be evaluated as soon as possible by a specialist known as a Urologist. If possible this should be a Uro-Gynecologist, as they are specialists in the urinary problems of women. That is the kind of doctor that can evaluate exactly why you are having problems getting the urine stream going.
Here is an essay written to explain some of the problems people with MS can have with Urination.
http://www.medhelp.org/health_pages/Multiple%20Sclerosis/The-Neurology-of-Bladder-Incontinence/show/758?cid=36
The second problem you have is with a doctor that leaves you out in the cold with regard to how you are to approach this disease. Giving you Copaxone was a good thing, but he should have begun the process of getting you educated on how to work with him to take the best care of you. He sounds lazy. I can't believe that a neurologist would make this diagnosis and begin Copaxone without making it very clear when you were to come back. Usually it is in a month or two to see how you are doing.
He should also have given you clear instructions on when to call his office with problems. The answer to that is anytime you are having symptoms that you don't understand.
What resources did he give you or recommend to you to become educated on this disease? If the answer is none, you need a new doctor who will actually take the responsibility for helping you to know this stuff. If you are like me, your MS did NOT come with a manual.
You must feel lost! Well, we all believe here that the more we know about this disease of ours, the better we can help ourselves and our doctors - and the healthier we will stay. Our whole purpose here, beyond friendship and support is to build our knowledge base, and educate others.
I hope you will stay with us and let us help you be active in learning what you need to know. We have some good articles written by people here on topics relating to MS. We can also point you to great resources for stuff.
In the meantime, get your urine tested and get a referral to a Uro(gyne)cologist. And check around to find a better neurologist.
Welcome again,
Quix