Yes, perfectly normal. A person's body weight will vary by as much as a few kilos over short periods of time due to retention of food, water, muscle and fat. The only sure way to determine if you're putting on weight is to measure your weight over a long period of time, say, two months and work out if there is an upward trend.
Also, if you are exercising then your muscles will bulk up to a certain point, and that will cause weight gain, or at least hide weight loss due to reduction in fat. Which is good, since muscles are active tissue and will "burn" more fat, even when not exercising.