Javascript Clicker Game İsn’t working / The click button is not working

Im trying to make a basic clicker game on JS. But theres a problem.

I tried to make a 2x clicker thing which is the game will ask you if you wanna buy 2x clicker when you reached to 100 clicks. 2x clicks will basically give you 2x clicks.

However i think it broked the entire code since click button is not giving any clicks.

Heres the codes:

JS:

let clickCount = 0;
let clickBoost = false;

document.getElementById("clickButton").onclick = function(){
    clickCount +=1;
    document.getElementById("clickCounter").innerHTML = clickCount;

    if (clickCount += 100){
        let boostyorn = prompt("You have more clicks than 100." + "n" + "n" + "Do you wanna buy 2x Clicks?" + "n" + "(Y/N)")
        if (boostyorn == "Y"){
            document.getElementById("clickCounter").innerHTML = clickCount - 100;
            clickBoost = true;
        }
        else{
            alert("You didn't bought 2x Clicks.")
        }
    }

    if (clickBoost == true) {
        document.getElementById("clickButton").onclick = function () {
            clickCount += 2;
            document.getElementById("clickCounter").innerHTML = clickCount;
    }
}

}

HTML:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Clicker</title>
    <link rel="stylesheet" href="style.css">
</head>
<body>
    <label id= "clickCounter">0</label><br>
    <center><button id= "clickButton">Click</button></center>
    <label id= "clickBoost"

    <script src="index.js"></script>
</body>
</html>

CSS:

#clickCounter{
    display: block;
    text-align: center;
    font-size: 150px;
}
#clickButton{
    display: block;
    text-align: center;
    font-size: 100px;
}