Is it normal that swimming makes me anxious and want to take drugs?

I've being swimming since I was six and swim 4km three days a week. I kept trying and working hard, I lost 20kg, I increased the number of days I swam and I exercised everyday.

But every effort I made seemed inadequate compared to all these young athletes I'm surrounded by. Every time I go to squad classes I feel a strong sense of anxiety, I need to breath heavy and the three hours leading up to swimming I spend trying to get into the 'zone'. The squad lesson starts okay but at about halfway I start noticing things: younger people are ahead of me, the coach is focusing on and helping the faster students and the coach doesn't even clue me in on what's next. Then a thought comes into my head: 'It doesn't matter what I do, I'm a waste of space to them, I'm just an extra to them.' That's when I give up and grovel in the toilets, feeling inadequate and frustrated. I started to take licit drugs (like strong flu tablets) thinking that if I'm somewhat 'not there' it will be easier to cope.

I love swimming, but hate having to compete or be compared to all these people who go five days a week and have being genetically gifted.