Your address may be associated with multiple transactions - incoming and outcoming - and all these transactions need to contain some information to be recognized by the network. The number of unspent transaction outputs depends on how many incoming transactions you have and how many of them have not been spent during other transactions. So, if you reuse an address, it may or may not contain additional UTXO since we take into account only unspent coins. For example, you receive 5 BTC in one transaction using your address X and later send it to address Y. As a result of such manipulations, you will have zero UTXOs associated with address X. If you use it again in another transaction to receive coins from address Z, your UTXO count will increase correspondingly.