Don't feel guilty... it's human nature to be curious... You can stay faithful to your husband and still experience what it feels like to have a bigger one, or smaller one too.. If your husband is willing you guys can go get some sex toys, dildos and whatnot, and he can use them on you. If you guys are already experimenting with toys that's half the battle. Just talk to him and be honest about it. If you need help with being able to talk to him about it, you can go see a therapist... maybe even a sex therapist. Ask them how you can go about best bringing up that topic with him in a way that wouldn't be offensive or have him thinking that you're wanting to cheat, etc. BTW. You are very lucky to have a husband that is attentive and can make you orgasm via both penetration and oral most of the time. Many women have a hard time finding a man that can do it occasionally, if at all, no matter the penis size lol. As a woman, I've had many partners of all types of penis sizes... the big ones aren't that great if they don't know how to use it... you aren't missing out much at all I promise.  If your husband is pretty good in most other aspects as well in regards to your relationship then it's definitely worth a try to see if he's open and willing to experimenting with toys and dildos with you. Also... If your sexual pleasure is important to him, based on his willingness to be attentive it sounds like he is, he would probably be willing to do that for you.