Hello, and welcome. I am a licensed attorney and happy to assist.
I'm sorry to hear of the situation, but happy to say that you likely have recourse. Since you were not properly served, you are correct that the judgments can be invalidated, but causing legal invalidation will take a little effort - it is not automatic. You will need to file a motion to set aside the judgment for failure of legal service, in each action in which a wrongful default judgment was awarded against you. If you lost on summary judgment after filing an answer, this will notapply because failure of service of process stops being an issue if you answer a complaint. But, where you did not answer, if you can show that you were not properly served, the judge will overturn the decisions, require proper service and allow the actions to go forward. The judgments should than be removed from your credit report. If you are successful in these actions, there will be no judgment entered against you at a later date. Taking prompt action is important if you want the court to grtant your request, because one of the factors considered is your diligence, upon finding out that these problems have occurred.
I hope this helps. If you need additional information or clarification, just let me know and I'll be happy to continue providing assistance. If I have addressed your issue and/or pointed you in a positive direction, please let me know that as well, and please remember to leave a positive rating when prompted, as that is the only way attorneys on this site are credited for the information we provide.