Frustrated and about to give up on sex

I am feeling frustrated and defeated with sex. Me (26m) and my wife (25f) have been married for 3 years and have sex maybe 1 or 2 times a month. Neither of us have ever been with anyone else. I try to make sure she always cums but I feel like I am very bad at sex. I can only last 1-2 minutes with PIV. I also have a hard time staying hard, usually when I go to put a condom on I get soft for some reason. I'm not sure if this is performance anxiety or what. I love eating her out but she usually doesn't cum even if I am doing it for 15+mins and then I think she just gets bored and tired of it and tells me to stop. Usually we have sex and then we use a vibrator for her. She likes when I hold the vibrator but I can never tell where to hold it and she has a very specific spot she wants it held. Also my arm and shoulder start cramping and shaking and then she gets frustrated because I'm moving my arm. Usually we both hold it together but even then she sometimes still gets frustrated. I also feel weird just laying next to her helping her hold her vibrator and not doing anything else. She won't let me kiss her or touch her while holding the vibrator so I kind of just lay their awkwardly and try to stay as still as possible. After 30mins to an hour if she still hasn't cum she usually kicks me out of the room to finish herself. I don't know what to do anymore as anytime I try to talk to her about sex she changes the subject or just avoids it. I would love to have sex more often with her and I feel like part of the reason she hardly ever wants sex is because I'm so bad at it even if she says I'm not. I don't know how to get better at it without her help, it's not like I can just go around sleeping with other people to get more practice and get better at it. I'm just really at a lose as to what else to do other than just give up on having sex at all. Does anyone have any helpful advice? Thanks