i think i might be getting engaged

I think my bf will be proposing in July on my birthday. I say this because #1 his father just passed and besides his mother he has no other family. His dad and I were really close and was even supposed to walk me down the aisle whenever the time came, we of course thought we had time and I never got the opportunity to ask him. #2 He has been telling me that he needs my sister to text him. He and my sister are close but not to the point where they talk everyday. The only time they really talk is if im on the phone and its on speaker or when she comes over.My sister just moved and started a new job so she's very busy and doesn't check her phone often so he'll say things like your sister needs to respond to my text". But what really makes me thinks it's going to happen is we were talking about weddings and I don't remember excatly what we were talking about but we were on the topic of engagements and he said "it's going to happen soo..... let me shut up" now my bf can keep a secret he has suprised me b4 and never let the beans spill but idk if he's too excited or what it is but the way he's been acting i may be right. Obviously I don't want to think about it too much but of course I'm one of those girls who has been thinking of her wedding day since I could spell the word wedding. He has told me many times even a few days ago "you can start planning " I definitely plan on marrying you. My question Is should I start planning or wait until an engagement happens? Oh and btw we've already agreed on date for next September 🤔