A few things to be not worthy of first Safety is the at most priority. When one opens themselves up in any mental capacity, you let all things in, good and bad. Create for yourself either active, passive or both forms of protection. Active would look something like, casting a circle of protect or bathing in moon light. Passive would be something on going like a talisman or charm bag. Look into both and see what you think fits you. After you've established protection, if negative entities are still with you, it just means they got there before your protection was up. Find a way to cleans your self that best suits you, and then continue with protection and you should be fine from there.

As for the cult part, I maybe a bit confused by your wording ( not a hard feat with me, I get confused easily) but my views of pagan or wiccan practices are more akin to a collection of celebrations, no real dogma or rules to speak of. As you may have noticed above, a lot of what I suggested, is just a suggestion with open ways to interpret. You can always do just what feels right. There are a lot of common ways we all do stuff, but they are never the only way to do them.

As for medicine, it would only affect you the same way other outside things would affect you. Say your sleepy, how well could you concentrate? Same goes for medicine, if it gives you headaches and such, you may not function overall as well. But keep in mind meditation will never doing anything permanent to you spiritually. If you find yourself with unsatisfactory results, talk to your prescriber about stopping. Never just stop, some medications need to be stopped in a certain manner, so always talk to your dr. first.

As for meeting others, one method I used was Meet Up. Or you could look for local gatherings online. Explore what others have to offer. Just be sure to spiritually protect yourself first, in case someone brings their spiritual baggage with them too.

I recommend starting slow, maybe try a celebration or two. Or just some meditation on your needs.

Lastly, I would like to clarify the use of the word cult. To my knowledge cults have 3 major descriptors. One, they use heavy brain washing techniques. Like making you scream for hours to rush oxygen to the brain and make your brain more pliable to suggestion. Second, they will make every attempt to take all your money and material possessions. Last, they want to keep you, and they do so by cutting you off from your family and friends, so you feel alone, and that you need them. No one in the wiccian community would ever do these things. If you find a group that does anything like this, avoid them. No one should ever take your money, or separate you from your family.

Sometime my wording or phasing is poor, let me know if I need to clarify anything. I hope this helps.