My Dog Has Developed Severe Allergies And Has Been On

My dog has developed severe allergies and has been on tablets from my vet 3 times. I hate giving her these tablets as she is a different dog while taking them. She is unwell and very lethargic. After the last course of tablets she suddenly refused to go for a walk. I have been making her go for short walks but she can't get home fast enough. She has also taken to sitting on my knee. You might say this is not unusual but previously she always found this to be too hot. Is her behaviour normal and is she just adjusting to my lifestyle.