10mg of methylphenidate is a low dose, most adults don't get much if any effect from that. So don't worry if it's not helping yet; that's quite normal. You just have to start on a small dose and work up, if you start on a higher one it often feels awful.
Be patient with titration, as it's important to get the dose right. It takes time to do this and on the way you'll go through lots which won't be quite right, or which might even make things temporarily worse. It's a good idea to be in a fairly stable place if possible when going through titration.
Then even when it is right it can be a bit rocky as you have to un-learn some unhealthy coping mechanisms you may have developed in order to learn better ones.
Headache is a common side effect and will go away as you get used to it. Take paracetamol for it, because it will probably persist for a few days and ibuprofen shouldn't be taken for longer than 3 days without medical advice.
Keep a diary - it helps to look back on this or bring it to your appointments. Record the date, dose, timing, drug and formation (e.g. extended release/instant).
If you're the kind of ADHD that likes information, I found this webinar/podcast very good, though I think his insistence that it has to be life-changing is a bit of an exaggeration.:
There is also this which tells you about how all the different medications work - quite sciency, avoid if that's boring. The long one is the same content as the part 1/2/3 etc, just all added together. https://www.youtube.com/playlist?list=PLKF2Eq0eYbbrWLf34RL1T9B27XCUuHCfB
The hangover feeling as it wears off is called Rebound. It's stronger with instant release because you're getting a big dump of the drug in your system which then all leaves your system at the same time. So when you change to an extended release format, which is usual, you should find this is less of a problem, as it tends to release more slowly which means it also leaves your system more gradually. If you're getting rebound, note it in the medication diary with a rough time. This should also ease off as you get used to being on medication.
IME it helps a lot if you can do other "good habits" things - enough sleep, regular food, staying hydrated all help the medication to work properly. If you just take your medication and then sit on MN you will probably find you hyperfocus on MN :) So having a rough plan or idea of things you want to try to improve on with medication, and then trying to do those things, can also be helpful - you can again comment on this in your diary.
It's not that uncommon to get mood changes (esp more anxiety, more irritable) but actually mood changes are a significant side effect you should report to your doctor, especially if you're experiencing feelings of depression or intrusive thoughts or thoughts of self harm - that's not a "wait for the appointment", that's "call them ASAP".
Your menstrual cycle can affect how effective a dose is, so once you start getting into the doses which are feeling effective, it's a good idea to try taking it over a longer period. Specifically the week leading up to a period you might experience worse ADHD symptoms or the medication might feel less effective. Also, if you haven't had a general health check up before starting the medication, it doesn't hurt to ask your GP for blood tests to check vitamin and thyroid levels. If you take a multivitamin or iron supplement containing vitamin C, make sure to take this in the evening as vitamin C can counteract the effects of ADHD medication.
Different people get different results from the different drugs, so reading about other people's experiences likely won't be that helpful, but for me, methylphenidate wasn't great and was more side effect than useful with increased anxiety and intrusive thoughts - mainly about social interaction, ie I'd go out and see my friends, and then the thoughts would plague me all evening "I can't believe I said that, what must she have thought of me???" even though I know logically that my friends would not think of me in that way. I also would get very focused into a task and then be furious when people tried to interrupt me, which doesn't help when you have young children! Elvanse is much better for me. I haven't tried any others.
The benefits I get from it are increased patience, better emotional regulation, less likely to get sucked into the vortex of online scrolling, more energy (I'm not exhausted at the end of every day) - in practical terms, I play with my children so much more, I don't snap at them anywhere near as much, I can do things like crafts with them and it doesn't end in disaster or destroy the house.