I did this last year (self-studied Calc, Gov, Micro/Macro (both), and Human Geo). It’s definitely possible, but you’re going to have to be pretty dedicated. A few months is enough time to study enough for all of them. Necessary? Maybe not. Feasible? Definitely, if you set your mind to it. For instance, I had to pretty much stop going to games and practices for the tennis team and instead worked inside review books and read through them.
What you need to do is learn material for the test. Not your curiosity. Not to fully learn a normal school’s curriculum at a class’s pace. You’re absorbing knowledge to regurgitate onto the AP exams in May.
Know that there are a lot of resources online. Look for study guides, review packets, and actual released tests online aside from your usual review books.
Get Larry Krieger’s Crash Course for Gov and do the practice tests. Krieger is a godsend for those AP Tests (I don’t know if it’ll be different, but his APUSH Crash Course/Insider’s Guide was ultra helpful as well). That’s pretty much all you need, but you can go to Barnes & Noble and look at practice tests from other review books as well.
Do all you can to know the basics of APHUG, but don’t spend too much time with the details; the exam I took had almost nothing about what I read in the review books and I ended up guessing on about 80% of the multiple choice.
If you’re picking between the two, pick Macroeconomics. It’s easier to learn, easier to understand, easier to memorize, and easier to take as a test (with a higher curve for a 5).
For English Language, practice writing essays. Seriously. Establish what stylistic choices you’ll be analyzing most, and be ready to write three essays on things you may have no interest in. The passages will be similar to SAT CR, except you’ll have to know a lot more about the technical stuff like notations, tone, etc.
Review books are your best friends, but sometimes they’re not enough. Immerse yourself in the material you’re learning because the class isn’t there to do that for you. Good luck!