Hi
You have a lot going on in your post. First, congrats: the only way to get experience is to get experience.
And your posts suggest you got a lot of it. Others have all ready commented on the motion sickness meds and made other positive suggestions . My experience with motion sickness meds is you want to start loading those about 24 hours ahead of diving. Read the ingredients of each, they are not all the same. Find the one that works best for you. Note, they can make some folks drowsy.
The main thing I would add as a suggestion/ mention, especially considering where you were diving, is to hydrate, hydrate, hydrate. You can not drink enough water. I know the mantra " don't pee in your wet suit" , but everyone has done it.
Your post also suggests a built in diving lesson for all of us; the importance of planning YOUR dive and diving YOUR plan. As others have mentioned, you can call a dive any time, after all it's your life.
Experience is the most important piece of "equipment" you will ever take on any dive. Speaking of equipment, having your own, being familiar with it, inherently is a confidence builder. Starting out you may still be undecided on how invested you want to be in diving. However, comfort/fun and enjoyment of diving are directly proportional to reducing task loading. Learning a dive site, sea conditions, using rented equipment and trying not to loose your buddy as a new diver about peg the stress meter.
Just starting out, keep it simple and keep it shallow. Soon enough you'll hear "the call of the deep" that we all have heard. Preparation and experience under water will be your best preparation.
And I guess lastly, It's natural to gravitate and rely on someone who has more experience than you underwater but ultimately you are responsible for you, not them.
If you feel comfortable with a DM or a shop or boat operator on land you'll probably have a better outcome underwater. If the vibe isn't there on the beach it wont be there underwater. There is a reason we have all been given common sense. Sounds as if you have gotten a lot to note in your log book. Good luck and dont skip those deco stops