Training for sprint but trying to build volume, too

I gave birth to my first baby in May (yay!) and started training a few weeks later; I registered for an Olympic tri in July last winter when I could still see my feet and felt brave! My goal was only to finish, and I did finish with a better time than I expected. My only goal in registering for races this summer was to get myself back in shape.

My next race is a sprint in early September, and this time I hope to actually compete in this one, though I absolutely don't expect a PR! I'm still relatively new to triathlon, and I could use some advice. I know that if I want to compete, I should train specifically for this distance. However, I still have weight to lose, and I want to build endurance as well. My normal training is a 22 mile hilly bike ride, 2000-5000 in the pool, and a 6 mile run. While pregnant, I rode my trainer and continued my normal run until I couldn't for medical reasons around 31 weeks (in February), and after that, I swam (slower every week) until I delivered in May. I resumed training when I was cleared to do so in June. Biking was easiest to resume for some reason; I'm back on track to very close to my pre-pregnancy pace. It was easy to get back to swimming distance, but I'm still incredibly slow. Running took the longest to get back because I had a C-section, but I'm building my pace faster than I'm re-building my pace swimming.

I'm kind of at a loss as to what I should be doing, and short of hiring a professional coach or trainer, I don't know who else to ask. Is it reasonable to do a short, fast workout in one discipline for race training, and then a long, slow one to build endurance and lose weight? For example, today I did a 3 mile run at a much faster pace than my race in July, and then an hour long pyramid in the pool. All three disciplines need work in terms of pace AND endurance, so I've been trying to work on both separately for each discipline.

I feel like I'm starting from scratch, but with an okay aerobic base, since I was allowed to keep working out for most of my pregnancy. But realistically, I slowed down in my first trimester last fall, stopped most training in February, and didn't resume until June. I've been a runner for nearly two decades, but I consider myself a newbie, middle of the pack triathlete. My goal right now is to start competing again, and to build towards my first half Iron distance next year...and to lose the baby weight. Any insight for the short and long term would be greatly appreciated!

Oh, and I joined a local tri club, which will definitely help. I've already met some very cool people to train with, and I'm sure I'll learn a lot. But I'd love some guidance for my individual workouts starting now, because I'm really winging it! TIA :-)