I'll save you my story (unless you indicate you want it), but I know your pain, your frustration and sorrow. My advice is for you to contact NAMI (National Alliance for Mental Illness) and sign up for their free Family to Family course for you and your son if he will attend. If not, you go on your own and get educated, encouraged and empowered.
I cannot emphasize enough for you to get education and support. Pray and have faith. If you are a believer, know that Romans 8:28 - God works for the good...
Draw your boundaries with your son. You said, "refuses to take medication" and "I don't know how to help him anymore." You cannot help someone who doesn't want the help and insists on doing it his way. Don't enable him and don't be his doormat. The best help is to be consistent, firm and one he can count on to help him manage finances, paperwork, MHMR, doctors, etc. when he is willing to use those services. That DOES NOT mean you bail him out of trouble.
Your heart will still be wrenched but you will not be as exhausted if you're not trying to bail him out of the messes he creates because he CHOOSES not to take medication, get counseling and take the steps necessary to manage his illness. Just like you can't save an alcoholic and keep him/her from drinking or people like me (from eating too much junk food)you can't force him into making right choices.
A friend's 28 year old son has bipolar and refuses medication. He's mostly manic and aggressive. he's punched holes in her walls, broken the glass in her hutch and is in and out of legal trouble. I have little compassion and patience for her because her actions are teaching him that it is OK to trash her home when he's angry. It frustrates me to listen to her talk about her son. You will wear out the support of your family and friends if you help your son stay in self-destructive behavior. I think it would be like me complaining that I can't understand why I'm not losing weight and how miserably fat I am as I spoon a carton of ice cream in my mouth. (I am fat and miserable about it but don't compalin because it is my own fault!)
It's tough parenting - I know. Allow him to suffer consequences and then be there for him when he is ready to listen and allow you to help him get and stay on the right track. It is unfortunate he has bipolar, it is not your fault he has the illness (even if you passed the gene to him). He needs the security of knowing when he is out of control you are stable and in control. Recall the toddler who needs the security in knowing a parent is consistent.
Learn all you can about bipolar. Read up on the latest medications. When your son is willing or he gets into legal trouble and a judge orders him to take medication, know about the drugs being prescribed. Question the doctor. Go to the manufacturer's website and read. Another post warned you about stimulants and medications that worsen the illness. You must advocate for your son even with a doctor because they often will prescribe a drug the manufacturer states is NOT for patients with bipolar.
May God bless you and comfort you. Parenting is the toughest job ever!