Long term effects of medication

I've been having a really bad episode of D that has lasted a couple of months. I have already started with calcium and peppermint tea in the morning and this has helped a little bit and I take paracetamol or ibuprofen for the pain. I went to my doctors and she thinks it's ibs we're waiting for the results of the tests I did but she seemed quite sure. She said that if it was she would start me on an antispasmodic medication and perhaps also loperamide because my D has been so bad it's really interfering with my life.But I'm just worried because I am only 19. I have so far stayed away from things like immodium because I'm scared to become dependent. If I start taking these medications and if they are effective won't my body build up resistance to them and they'll stop working?? I don't want to end up 10 years down the line realising I've built up an immunity to the meds and my ibs is even worse!