Puppy peeing inside at 5 months

My puppy is 5 months old now, me and my bf have had her for around 2 months at this point and she’s been making such good progress in all areas to imagine, but there’s one issue that’s nagging me. She’s pretty much fully housetrained, meaning she never pees inside except for accidents. But every time we’re about to go for a walk or she sees us preparing for a walk and we call her name she pees herself. She can’t hold it in and she just starts peeing or sometimes it comes a little. This is pretty much every time we’re about to go for a walk and I have no idea what we’re supposed to do. I’m so tired and my mind just tells me that this is something that’s always going to be a problem with her. I don’t know if this is common for 5 months puppies either. Ive had three dogs in my life and none of them have been this bad. At first I thought “well, she’s got a small bladder and it’ll get better” but now I’m starting to think it might be some underlying condition. She drinks excessively much water, all the time and it just feels like she constantly needs to pee. Maybe it’s a UTI but I don’t know, could it be submissive peeing? I just need to vent because every time she pees inside it just feels like a huge step back rn.