Determined to Finally Get Fit and Healthy, on a Journey

So I just turned 30 and about 5 months ago I finally decided to get fit and healthy which started my changing what I eat and joining a gym. I've lost 20 lbs (which has flucuated over the past month) and haven't lost anything in the last month at least but I know that I'm feeling and looking better, my clothes are fitting better and looser and people are noticing the changes.
I post on Instagram for my friends about my workouts and food as part of accountability and to see my progress and put it out there that I'm gonna do this!

I know this will be a long journey and I'm trying to remember that and be determined and patient plus keep my motivation especially since I haven't lost anything weight wise however I did just have a friend measure me which I should have done in the beginning, oh well!
So I'm going to turn to all of you guys I hope and the forums to give me some more encouragement. It really helps to see people who have been successful with losing weight the right way with eating healthily and with exercise.

A little history on me: I've been overweight my whole life (since I was 5 or 6 I guess) but there have been heavier times with the most recent being this past year (end of last year and also was this weight some years ago maybe around 2006-7 (the highest being maybe 315 and I'm 5'7 by the way ). Over the last 10 years the lowest I've gotten down to was maybe 230, I can't recall but the most recent I recall being smaller was 3 years ago when I moved to where I am now and it was not intentional that I recall and then a year later my weight went up and up until 5 months ago when I took control.

I've been aiming to get to the gym 6 days a week and successful with that quite often for the last 2 months and at least do 3-5 days. But I started at the gym about 5 months ago and made it 2-5 times a week. I use machines with weights and cardio involving either the treadmill with intervals and I try to do HIIT as well as on the elliptical which gives me a great workout.
I've stopped drinking pop in these 5 months and really any sugary drinks I avoid as well as less coffee and more tea. If I drink coffee I try to get skim milk or nothing and a bit of sweetner but cutting out the fake stuff too now so mainly I drink water and lightly sweetned tea or no sweetness at all and other herbal teas or coconut water.
I eat little fried foods even though I still eat out often I choose healthier options and rarely eat red meat. I've also cut back on eating bread and getting in more veggies and fruits though I still have a long way to go with integrating them fully into my life as I'd like to eat mostly fruit and veggies and less processed stuff, but for now I'm doing way better than I have in the past. I do eat frozen kashi meals mostly if I do and my goal is to cook way more but I'm working on that.

So at this point I've gone down at least a dress size and I feel good and I can feel the difference in how my body feels size wise but I haven't lost any more weight recently and I'm wondering why. I know the number isn't as important as other changes but the number is important still, Am I at a plateau already? I've been doing the elliptical more than the treadmill for the last month, should I switch back to treadmill for awhile or I was thinking of switching every other day.
I'll probably post under another section to get some answers but looking forward to gleaning from everyone and hopefully encouraging others as well. I have the ultimate goal to lose 100 lbs and I know it's going to be a long, tedious, difficult journey, but I know it is worth it and I know I can do it.
We can do it!

Thanks.