Can my tubes come untied by having hard sex?

No : Tubes are not 'Tied' - they are cut. Usually several centimeters are removed and each end is cauterized. Sex would not undo this process. Depending upon the surgeon and where your surgery was done, different results and risks may be at play. You should consult with the surgeon/Gyn whom provided the service to discuss what exactly was done in your partiuclar case.