MySQL connector PreparedStatement->setString not working C++ - c++

Question

So, basically all this code does is search the database for a user with a certain username and password, and returns a nullptr if it doesn't find one.
Gebruiker* Gebruiker_DAO::getGebruiker(string login, string wachtwoord)
{
PreparedStatement *prep_stmt = nullptr;
ResultSet *res = nullptr;
Gebruiker* gebruiker = nullptr;
int rowcount = 0;
try {
prep_stmt = dbConn->getConnection()->prepareStatement("SELECT * FROM Gebruiker WHERE Gebruiker_login = ? AND Gebruiker_wachtwoord = ?");
prep_stmt->setString(1, login);
prep_stmt->setString(2, wachtwoord);
res = prep_stmt->executeQuery();
while (res->next()) {
gebruiker = new Gebruiker(login, res->getBoolean("Gebruiker_isAdmin"), res->getString("Bedrijf"),res->getBoolean("Gebruiker_isActief"),res->getInt("Werknemer_ID"));
}
}
catch(SQLException& e) {
console.log(e.what(), console.Error);
return nullptr;
}
return gebruiker;
}
The issue is that setString throws an "std::bad_alloc at memory location ..."
Ive noticed before that trying to put a string in an SQLString also throws an error. Until now ive used a workaround by putting stuff in SQLStrings.
SQLString schema = "groep003B";
dbConn->getInstance()->setSchema(schema);
dbConn->getInstance()->connect();
For some weird reason this DOES work...
Is there something i am doing wrong? I have seen examples where people use strings, but for some reason this does not work for me... Every time i try to put a variable std::string in an SQLString it gives a memory issue.