It sounds like you answered your own question--maybe he just needs more arousel. It sorta sounds like you quickly get naked and want to jump right into things. That seems to work when you are 18 but you didn't say how old he and you are. Perhaps try sleezing up to him for a while first. Find out which things turn him on and do them.
Do you know as we get older, our sexual drive slowly declined, in my opinion ,ED is start kicking in. In any committed relationship sex is important and while a relationship is made up of many other elements as well sex really solidifies the love and commitment between two people. Being in a relationship without sex simply drains the life out of the relationship, so if erectile dysfunction (ED) is a problem it is important to get help as quickly as possible. This may not only save your sex life, but it might also save your relationship.
This is not uncommon, especially as guys get a little older. The difference is, when he's turned on by himself, there's no pressure to 'perform' - he's not worried he's gonna lose the erection, and if he did, would just start stimulating himself again to bring it back. Guys can become overly self-aware of their erection & the minute he starts worrying about keeping it, it goes down. I think the solution hinges on good communication, tell him you love him & are very attracted to him (hopefully true!), and maybe try some other forms of sexual activity, like manually stimulating each other, oral, etc., and try to get the fun back into it. If he's having fun & enjoying things, without pressure to 'perform', he'll be looking forward to your time together & not worrying so much about how well he's going to do. Women think guys always have sex on their minds (which is mostly true) & that therefore they should be ready for it at any time, and that's true at younger ages, but later on, he may need a little more stimulation & keeping things fun & interesting. Just make sure he never feels you're pressuring him for sex. I hope that helps...
You sound like you are willing to do whatever it takes to turn your husband on. LUCK HIM!! I struggle a little with a really hard erection since a robotic prostatectomy. My women PA healthcare professionals keep telling me to masturbate often to restore it. Eeven bought an artificial sex toy ***** and *** that my wife helped pick out. Not all that! No substitute for my wifes vagina. You said he got arroused at the pool? Game on girl! I'm sure you can be and are the sexiest women in his life! Dress sexy, wear skimpy bathing suits at the pool! My wife does and I can't keep my eyes off of her at 60 yrs old! PUT EXCITEMENT BACK IN YOUR LIFE! Thats what a husband needs! Be risky. My wife actually took her top off riding down the road. I GOT SO HARD! So what if another guy saw her. That is part of the excitement and ok! My wife even masturbated in front of me! I-loved it! Fantisize!! NO HARM IN THAT! Brings sensuality back in your marriage. Nothing a husband likes more than seeing his wife walk around the house naked. Even better, go outside naked. My shy wife even let me take nude pics of her spread eagle and bending over. Husbands love that possition!! HE WILL BE SO HARD FOR YOU! Be risky and have fun! You are the best thing-that ever happened to your husband!