Why do you think the universe expanding means that its being stretched out? Thats the only reason why you would think the universe expanding must mean everything in the universe must expand too.
It doesnt work that way though.
Also, the Earth is where it is in the solar system due to gravitational pulls from not only the sun, but also all the other planets in the solar system. The sun is the strongest force of gravitational pull and it pulls us in one direction. But them smaller forces like Mars pulls us in another direction. And ofcourse, the big mfer Jupiter pulls us in another direction. All these forces are pulling us in different direction, but it all evens out in this spot we are in, which is why the earth is where it is.
And the Earth didnt just appear out of thing air. At first, there was dust and gas all over the place and they all of that got pulled and pushed in different directions until millions of years later gravity kept pulling them together and they started being pounded into each other until the earth was formed.
So, at the very beggining, the earth was a different size, but really, the earth wasnt the earth yet. After millions of years of the dust and rock being pushed and pulled, the earth was finally formed. The continents were in different places, the atmosphere was different, there wasnt a moon, etc.
Once the earth became the earth that we know, it stopped growing. The earth doesnt expand just because the universe does.