Copying of entire articles, as you've described, doesn't fall within the fair use exception. Since you've already sent a DMCA takedown notice and received a counter notification, your next step is to file a copyright infringement lawsuit, or at least have a lawyer send a cease and desist letter threatening as much to the infringer. The counter notification should have included
(D) The subscriber’s name, address, and telephone number, and a statement that the subscriber consents to the jurisdiction of Federal District Court for the judicial district in which the address is located, or if the subscriber’s address is outside of the United States, for any judicial district in which the service provider may be found, and that the subscriber will accept service of process from the person who provided notification under subsection (c)(1)(C) or an agent of such person.
That information tells you which district court to file suit in and the alleged infringer has waived any argument that the court lacks personal jurisdiction over them. 17 U.S.C. 512(g)(3)(D). Further, the statute allows you to seek statutory damages in lieu of actual damages. Statutory damages are set by the court and range between $750 and $30,000 per infringed work with the potential to be increased to up to $150,000 per infringed work when the infringement is found to be willful. 17 U.S.C. 504(c)(1)-(2). You may also be able to recover your costs and attorneys fees, but this is at the discretion of the judge. 17 U.S.C. 505.
There are some circumstances where the hosting site can also be liable for the infringement, but those claims are difficult to win. Ultimately, you should consult an attorney to discuss your claim in more detail. You definitely have not forfeited or waived your claim, nor does the amount of time you've waited so far create an estoppel claim.