A few things that are useful to know when you go back to your doctor (I'm on a medical editorial team that writes about ADHD, so general info only):

• The two drugs work on different timelines. Methylphenidate acts within an hour or so, but people almost always start on a low dose and go up step by step, so day 4 is often still below the dose that works for you. Atomoxetine is the opposite: it builds up slowly and often needs 4-8 weeks, sometimes longer, before the full effect shows.
• "Working" is often quieter than people expect. Many describe it less as feeling different and more as: starting tasks with less friction, fewer half-finished things, not losing the thread in conversations. It's easy to miss from the inside.
• A tiny daily log helps a lot. Dose and time taken, hours slept, focus 1-10, appetite, mood, anything odd (heart racing, trouble sleeping). Two weeks of notes makes the follow-up appointment much more productive than "I'm not sure anything is happening".
• Sleep and caffeine can mask the effect. Short sleep makes almost any ADHD med look like it isn't doing much, and a lot of coffee on top of a stimulant can just feel jittery rather than focused.

The dose and combination are really your doctor's call, but going back with specific notes is the fastest way to get it adjusted. Good luck, it often takes a few rounds to get right.