Joint custody is very common and most judges do it routinely.
The magic words "joint custody" are pretty meaningless, as the detailed language of a parenting plan actually determine what rights you do and do not have.
You did poorly before because of not having a lawyer.
To change custody you have to show a reason, and a lawyer certainly can help present those reasons if they exist.
The likelihood of you obtaining "joint custody" depends on how you are defining the phrase. Joint LEGAL custody is preferred and is usually granted absent a showing that one parent is a detriment to the children. True joint PHYSICAL custody, defined as the child spending approximately 50% of each year with each parent, is difficult to obtaining; especially where the parents reside in different states. Shared physical custody (large amounts of visitation) is possible to obtain.
Unfortunately, obtaining the custody arrangements you want would've been easier than changing the existing order will be. This is because the first requirement in modifying an existing order is showing that there has been a change in circumstances since the initial order. When the modification being requested is custody, you show a change by showing that visitation has been frustrated (custodial parent interference), that the child's life has changed in some manner (grades slipping, behavioral issues, changed educational or other needs, etc.), that the parent(s) life has changed in some manner (homeless, medical issue, etc), or some other occurrence since the initial order.
It appears that you received bad advice from the attorney that you spoke to at the time of your divorce. I suggest that you speak to a few different attorneys about changing custody to find one that you're comfortable working with (or to a 2-way or 3-way consensus that your goal is futile based on the circumstances of your case).
The above answer is a general explanation of legal rights and procedures. It does not constitute legal advice. Nor does it establish an attorney-client relationship between the individual posting the question and the attorney providing the answer.