Thanks for posting your query at DoctorSpring.com
Frankly, with the sexual history described, you should not have lax vaginal walls.
It takes more than one vaginal childbirth to actually have walls that are so loose that you cannot feel anything during sex.
Is it possible that your partner did not have an erection that was hard enough , is that likely ?
You can confirm if the walls are loose by having an internal exam done by a Specialist OB - GYN.
This may rarely happen at your age due to some inherent weakness in the connective tissue of the vaginal wall.
It can then be surgically corrected ( the vagina tightened ).
All the best
Please feel free to discuss further.