Best of luck with your weightloss journey, and I hope that you are able to get a lot of support from this forum. Generally, I have found that people on here are so supportive and encouraging and it really helps to keep my motivation levels up!
I hope you enjoy your gym membership - I took up swimming this year and it's really helped me to lose weight. I try and swim between 2-5 times a week for about an hour or an hour and a half, and I have lost 7kgs since January. So a big shout-out to the benefits of swimming! I'm a fairly useless swimmer too, but I figure it all counts as exercise, no matter how slow I am or how uncoordinated I am
Re: gains and plateaus:
They are SO frustrating! I have been pretty lucky on the whole so far and have managed to avoid long-term gains, but I have definately gone through stages where my weight has hit a plateau. Between Sept-December last year, I was really losing motivation and I lost hardly anything. Admittedly, a lot of that was self-inflicted, as I wasn't eating well and I wasn't exercising as much as I should have been. The most important thing is to KEEP GOING no matter what, and eventually you will get your motivation back, and you'll be able to break your plateau. It really sucks when you are eating well and exercising and you hit a plateau, but I have noticed that most plateaus tend to occur when we think we are doing well and we slacken off a bit, allow ourselves extra treats etc....
Another tip: Whenever I am frustrated about the scales not moving, I reassess my diet and exercise choices. Am I eating well? Have I been eating too much? Have I been snacking? Is there a reason for the gain? Have I been exercising? If i find that there is no "reason" for the weight gain, I try and reassure myself that I am doing everything I possibly can to lose weight, and that the scales will start to move again in time. If I am being honest and accurate, the weight will have to come off eventually!! It's just a matter of persevering until it does
Don't stress about eating too much 'junk' over your birthday, it only happens once a year and you should enjoy it! Don't let your birthday celebrations extend too far on though, and get back into your regular diet and exercise habits ASAP. We all have moments where we eat 'forbidden foods', but the key is not to beat yourself up to it, and just put it behind you. If you have a particular food that is a weakness for you, try and incorporate a little of it into your diet so you feel less tempted by it and therefore less likely to binge later on. E.g. I love chocolate, but instead of sitting down with a family sized block (sad, but true - I used to think nothing of eating one of those in one sitting), I now just have a few squares or a chocolate biscuit at night instead to keep the cravings away.
All the best for your weighin next week, I look forward to seeing your progress! Don't ever give up