If you blaspheme the Father and repent, you will be forgiven.
If you blaspheme His Son Jesus Christ and repent, you will be forgiven.
But if you blaspheme the Holy Spirit, you cannot be forgiven. It is the Holy Spirit who convicts us of sin. The Holy Spirit lets us know when we've done something wrong and makes us feel guilty about it. Basically, if you feel guilty or are worried that you have committed this sin, then it means you haven't. If you haven't committed this sin, then all of your sins can be forgiven and you can be saved!