You may be aware that your case should be governed by directive 2004/38/EC concerning the right of freedom of movement of EU citizens and their family members.
Chapter VI of the directive says this:
RESTRICTIONS ON THE RIGHT OF ENTRY AND THE RIGHT OF RESIDENCE ON GROUNDS OF PUBLIC POLICY, PUBLIC SECURITY OR PUBLIC HEALTH
1. Subject to the provisions of this Chapter, Member States may restrict the freedom of movement and residence of Union citizens and their family members, irrespective of nationality, on grounds of public policy, public security or public health. These grounds shall not be invoked to serve economic ends.
2. Measures taken on grounds of public policy or public security shall comply with the principle of proportionality and shall be based exclusively on the personal conduct of the individual concerned. Previous criminal convictions shall not in themselves constitute grounds for taking such measures.
The personal conduct of the individual concerned must represent a genuine, present and sufficiently serious threat affecting one of the fundamental interests of society. Justifications that are isolated from the particulars of the case or that rely on considerations of general prevention shall not be accepted.
I am skipping paragraphs 3 and 4, as well as articles 28 and 29, as they are not particularly relevant to your situation.
Notification of decisions
1. The persons concerned shall be notified in writing of any decision taken under Article 27(1), in such a way that they are able to comprehend its content and the implications for them.
2. The persons concerned shall be informed, precisely and in full, of the public policy, public security or public health grounds on which the decision taken in their case is based, unless this is contrary to the interests of State security.
3. The notification shall specify the court or administrative authority with which the person concerned may lodge an appeal, the time limit for the appeal and, where applicable, [...].
(The last bit of paragraph 3 is not applicable in your case.)
You write that you do not understand why you were rejected. You therefore don't seem to have received a "precise and full" account of the grounds for your application's refusal. This raises a question:
Did you apply for your visa under the freedom-of-movement rules as a family member of an EU citizen?
Such applications are free of charge, so if you paid an application fee, your application may have been considered as a normal Schengen application, which might explain the uninformative refusal you received. If this is the case, you may want to reapply under the directive so you can get more information about the reasons for your refusal. You may also be able to invoke the directive in your appeal even if you did not make it clear in your initial application that it applies to you.
You should almost certainly consult with a lawyer to decide what your next steps should be. A lawyer will know the most effective route for getting the information that you should have received about the grounds of refusal, and about the most effective strategy, considering the grounds cited, to get you a visa by way of an appeal or a new application.