Actually, the thinner you are the slimmer the clothing you should wear. You need to accentuate your thinness. Wearing baggy or larger clothing looks worse. It looks like you are swimming in clothes or wearing your dad's suit.
People don't shop at Zara because they can get a jacket for 100 that looks similar to some designer jacket for 4000. In fact, the people do not even know that the 4000 jacket exists because they do not shop for clothes that expensive. People buy the Zara jacket because they like the jacket. Brand is irrelevant.
And actually looking at your height and weight above makes me think you will probably be in a larger suit than you think. I weigh less than you but am over 6' and often fit into 38. The only way to know what fits is to try stuff on.