Trouble coming without penetration

Hi guys !!! I've been kind of stressing about this and figured I'd ask have to see if anyone else has experienced something similar.

Basically, since | started using dildos regularly, I've noticed that I can't seem to finish anymore during masturbation unless there's some form of penetration involved. Before that, it wasn't an issue at all. Now I'm wondering if I've somehow "trained" my body in a weird way :( Has anyone gone through this? Is it just a matter of changing habits again or is this something 1 should be concerned about? Thanks in advance !!!